[docs] add component comments

Author: metonym

site/content/docs/02-template-syntax.md

@@ -165,6 +165,19 @@ Comments beginning with `svelte-ignore` disable warnings for the next block of m
 <input bind:value={name} autofocus>
 ```
 
+---
+
+You can document components with the `@component` tag. Component comments will appear when hovering over a component in an editor using the [Svelte Language Server](https://github.com/sveltejs/language-tools).
+
+```sv
+<!--
+@component
+This is a component description.
+
+@example <HelloWorld />
+-->
+<h1>Hello world</h1>
+```
 
 ### {#if ...}