Add documentation about the new supported HTML comments

Author: fnune

docs/README.md

@@ -43,6 +43,35 @@ It's also necessary to add a `type="text/language-name"` or `lang="language-name
 </style>
 ```
 
+## Documenting components
+
+To add documentation on a Svelte component that will show up as a docstring in
+LSP-compatible editors, you can use an HTML comment with the `@component` tag:
+
+```html
+<!--
+ @component
+ Here's some documentation for this component. It will show up on hover for
+ JavaScript/TypeScript projects using a LSP-compatible editor such as VSCode or
+ Vim/Neovim with coc.nvim.
+
+ - You can use markdown here.
+ - You can use code blocks here.
+ - JSDoc/TSDoc will be respected by LSP-compatible editors.
+ - Indentation will be respected as much as possible.
+-->
+
+<!-- @component You can use a single line, too -->
+
+<!-- @component But only the last documentation comment will be used -->
+
+<main>
+  <h1>
+    Hello world
+  </h1>
+</main>
+```
+
 ## Troubleshooting / FAQ
 
 ### Using TypeScript? See [this section](./preprocessors/typescript.md#troubleshooting--faq)