module: add docs signature for register

doc/api/module.md

@@ -80,15 +80,27 @@ isBuiltin('fs'); // true
 isBuiltin('wss'); // false
 ```
 
-### `module.register()`
+### `module.register(specifier[, parentURL[, options]])`
 
 <!-- YAML
-added: REPLACEME
+added: v20.6.0
 -->
 
-In addition to using the `--experimental-loader` option in the CLI,
-loaders can be registered programmatically using the
-`module.register()` method.
+* `specifier` {string} customization hooks to be registered; this should be the
+  same string that would be passed to `import()`, except that if it is relative,
+  it is resolved relative to `process.cwd()`
+* `parentURL` {string} if you want to resolve `specifier` relative to a
+  different base than `process.cwd()`, such as `import.meta.url`, you can pass
+  that URL here
+* `options` {Object}
+  * `data` {any} Any arbitrary, cloneable JavaScript value to pass into the
+    [`initialize`][] hook
+  * `transferList` {Object\[]} \[transferrable objects]\[] to be passed into the
+    `initialize` hook
+* Returns: {any} returns whatever was returned by the `initialize` hook
+
+Register a module that exports hooks that customize Node.js’ module resolution
+and loading behavior.
 
 ```mjs
 import { register } from 'node:module';