doc: reduce header nesting in async_hooks.md

Maximum header level reduced to 5.

PR-URL: #37839
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Pooja D P <Pooja.D.P@ibm.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: Trott

doc/api/async_hooks.md

@@ -25,9 +25,7 @@ as the abstract concept that is a resource.
 If [`Worker`][]s are used, each thread has an independent `async_hooks`
 interface, and each thread will use a new set of async IDs.
 
-## Public API
-
-### Overview
+## Overview
 
 Following is a simple overview of the public API.
 
@@ -79,7 +77,7 @@ function destroy(asyncId) { }
 function promiseResolve(asyncId) { }
 ```
 
-#### `async_hooks.createHook(callbacks)`
+## `async_hooks.createHook(callbacks)`
 
 <!-- YAML
 added: v8.1.0
@@ -133,7 +131,7 @@ Because promises are asynchronous resources whose lifecycle is tracked
 via the async hooks mechanism, the `init()`, `before()`, `after()`, and
 `destroy()` callbacks *must not* be async functions that return promises.
 
-##### Error handling
+### Error handling
 
 If any `AsyncHook` callbacks throw, the application will print the stack trace
 and exit. The exit path does follow that of an uncaught exception, but
@@ -150,7 +148,7 @@ future. This is subject to change in the future if a comprehensive analysis is
 performed to ensure an exception can follow the normal control flow without
 unintentional side effects.
 
-##### Printing in AsyncHooks callbacks
+### Printing in AsyncHooks callbacks
 
 Because printing to the console is an asynchronous operation, `console.log()`
 will cause the AsyncHooks callbacks to be called. Using `console.log()` or
@@ -176,12 +174,12 @@ provided by AsyncHooks itself. The logging should then be skipped when
 it was the logging itself that caused AsyncHooks callback to call. By
 doing this the otherwise infinite recursion is broken.
 
-### Class: `AsyncHook`
+## Class: `AsyncHook`
 
 The class `AsyncHook` exposes an interface for tracking lifetime events
 of asynchronous operations.
 
-#### `asyncHook.enable()`
+### `asyncHook.enable()`
 
 * Returns: {AsyncHook} A reference to `asyncHook`.
 
@@ -197,7 +195,7 @@ const async_hooks = require('async_hooks');
 const hook = async_hooks.createHook(callbacks).enable();
 ```
 
-#### `asyncHook.disable()`
+### `asyncHook.disable()`
 
 * Returns: {AsyncHook} A reference to `asyncHook`.
 
@@ -207,13 +205,13 @@ be called again until enabled.
 
 For API consistency `disable()` also returns the `AsyncHook` instance.
 
-#### Hook callbacks
+### Hook callbacks
 
 Key events in the lifetime of asynchronous events have been categorized into
 four areas: instantiation, before/after the callback is called, and when the
 instance is destroyed.
 
-##### `init(asyncId, type, triggerAsyncId, resource)`
+#### `init(asyncId, type, triggerAsyncId, resource)`
 
 * `asyncId` {number} A unique ID for the async resource.
 * `type` {string} The type of the async resource.
@@ -240,7 +238,7 @@ clearTimeout(setTimeout(() => {}, 10));
 Every new resource is assigned an ID that is unique within the scope of the
 current Node.js instance.
 
-###### `type`
+##### `type`
 
 The `type` is a string identifying the type of resource that caused
 `init` to be called. Generally, it will correspond to the name of the
@@ -263,7 +261,7 @@ It is possible to have type name collisions. Embedders are encouraged to use
 unique prefixes, such as the npm package name, to prevent collisions when
 listening to the hooks.
 
-###### `triggerAsyncId`
+##### `triggerAsyncId`
 
 `triggerAsyncId` is the `asyncId` of the resource that caused (or "triggered")
 the new resource to initialize and that caused `init` to call. This is different
@@ -302,7 +300,7 @@ that information, it would be impossible to link resources together in
 terms of what caused them to be created, so `triggerAsyncId` is given the task
 of propagating what resource is responsible for the new resource's existence.
 
-###### `resource`
+##### `resource`
 
 `resource` is an object that represents the actual async resource that has
 been initialized. This can contain useful information that can vary based on
@@ -316,7 +314,7 @@ could contain the SQL query being executed.
 In some cases the resource object is reused for performance reasons, it is
 thus not safe to use it as a key in a `WeakMap` or add properties to it.
 
-###### Asynchronous context example
+##### Asynchronous context example
 
 The following is an example with additional information about the calls to
 `init` between the `before` and `after` calls, specifically what the
@@ -415,7 +413,7 @@ TCPSERVERWRAP(5)
   Timeout(7)
 ```
 
-##### `before(asyncId)`
+#### `before(asyncId)`
 
 * `asyncId` {number}
 
@@ -432,7 +430,7 @@ asynchronous resources like a TCP server will typically call the `before`
 callback multiple times, while other operations like `fs.open()` will call
 it only once.
 
-##### `after(asyncId)`
+#### `after(asyncId)`
 
 * `asyncId` {number}
 
@@ -442,7 +440,7 @@ If an uncaught exception occurs during execution of the callback, then `after`
 will run *after* the `'uncaughtException'` event is emitted or a `domain`'s
 handler runs.
 
-##### `destroy(asyncId)`
+#### `destroy(asyncId)`
 
 * `asyncId` {number}
 
@@ -454,7 +452,7 @@ made to the `resource` object passed to `init` it is possible that `destroy`
 will never be called, causing a memory leak in the application. If the resource
 does not depend on garbage collection, then this will not be an issue.
 
-##### `promiseResolve(asyncId)`
+#### `promiseResolve(asyncId)`
 
 <!-- YAML
 added: v8.6.0
@@ -485,7 +483,7 @@ init for PROMISE with id 6, trigger id: 5  # the Promise returned by then()
   after 6
 ```
 
-#### `async_hooks.executionAsyncResource()`
+### `async_hooks.executionAsyncResource()`
 
 <!-- YAML
 added:
@@ -543,7 +541,7 @@ const server = createServer((req, res) => {
 }).listen(3000);
 ```
 
-#### `async_hooks.executionAsyncId()`
+### `async_hooks.executionAsyncId()`
 
 <!-- YAML
 added: v8.1.0
@@ -584,7 +582,7 @@ const server = net.createServer((conn) => {
 Promise contexts may not get precise `executionAsyncIds` by default.
 See the section on [promise execution tracking][].
 
-#### `async_hooks.triggerAsyncId()`
+### `async_hooks.triggerAsyncId()`
 
 * Returns: {number} The ID of the resource responsible for calling the callback
   that is currently being executed.