Merge pull request #2633 from zlsa/patch-2

Add barebones description of `svelte/register`

site/content/docs/03-run-time.md

@@ -556,9 +556,31 @@ You can see a full example on the [animations tutorial](tutorial/animate)
 
 * TODO could have nice little interactive widgets showing the different functions, maybe
 
+
 ### `svelte/register`
 
-TODO
+To render Svelte components in Node.js without bundling, use `require('svelte/register')`. After that, you can use `require` to include any `.svelte` file.
+
+```js
+require('svelte/register');
+
+const App = require('./App.svelte').default;
+
+...
+
+const { html, css, head } = App.render({ answer: 42 });
+```
+
+> The `.default` is necessary because we're converting from native JavaScript modules to the CommonJS modules recognised by Node. Note that if your component imports JavaScript modules, they will fail to load in Node and you will need to use a bundler instead.
+
+To set compile options, or to use a custom file extension, call the `register` hook as a function:
+
+```js
+require('svelte/register')({
+  extensions: ['.customextension'], // defaults to ['.html', '.svelte']
+	preserveComments: true
+});
+```
 
 
 ### Client-side component API
@@ -569,8 +591,6 @@ TODO
 const component = new Component(options)
 ```
 
----
-
 A client-side component — that is, a component compiled with `generate: 'dom'` (or the `generate` option left unspecified) is a JavaScript class.
 
 ```js