chore: Port FreeSewing.dev to docusaurus

The replaces the NextJS site powering FreeSewing.dev with a Docusaurus
setup. It's part of my efforts to simplify FreeSewing's setup so we can
focus on our core value proposition.

sites/dev/docs/reference/api/pattern/on/readme.mdx

@@ -0,0 +1,40 @@
+---
+title: Pattern.on()
+---
+
+The `Pattern.on()` method allows you to attach a function to one of the
+pattern's [lifecycle hooks](/reference/hooks/). It takes the
+lifecycle hook's name as the first argument and the function as the second.
+This method will then be triggered by the lifecycle hook.
+
+:::noteThis method is chainable as it returns the Pattern object:::
+
+## Pattern.on() signature
+
+```js
+Pattern pattern.on(string hook, function method)
+```
+
+:::tip
+
+Refer to [the Lifecycle hooks documentation](/reference/hooks/) for a list
+of all available lifecycle hooks, as well as the signature of the function you
+should pass it.
+
+:::
+
+## Pattern.on() example
+
+```js
+pattern.on('preRender', function(svg) {
+  svg.style += "svg { background: yellow;}";
+})
+```
+
+Your pattern now has a yellow background.
+
+:::tip
+
+The [plugin guide](/guides/plugins/) contains more info on how you can use hooks
+
+:::