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/plugins/readme.mdx

@@ -0,0 +1,40 @@
+---
+title: Plugins
+---
+
+FreeSewing uses a modular approach where functionality can be extended with
+plugins. Plugins can provide [snippets](/reference/snippets), 
+[macros](/reference/macros), [store methods](/reference/store-methods), or 
+use any of the [lifecycle hooks](/reference/hooks).
+
+## Using plugins
+
+Plugins can be either
+[added to part configurations](/reference/api/part/config/plugins) in designs or
+[added to a pattern instance with Pattern.use()](/reference/api/pattern/use).
+
+To import a plugin for use:
+```js
+import { plugin } from { @freesewing/plugin-gore }
+```
+
+:::tip
+
+For convenience, each plugin is exported as several names exports:
+
+- `plugin`
+- `pluginName`
+- `namePlugin`
+
+For example, `@freesewing/plugin-gore` has named exports `plugin`, `pluginGore`, and `gorePlugin` that all are the same thing.
+
+:::
+
+## Plugins we maintain
+
+<ReadMore />
+
+## Notes
+
+Refer to [the plugin guide](/guides/plugins) for an in-depth look into
+plugins.