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/addpart/readme.mdx

@@ -0,0 +1,48 @@
+---
+title: Pattern.addPart()
+---
+
+The `Pattern.addPart()` method allows you to add a part to a pattern.
+It has the same effect as passing a part to the Design constructor.
+
+:::noteThis method is chainable as it returns the Pattern object:::
+
+## Pattern.addPart() signature
+
+```js
+Pattern pattern.addPart(object part)
+```
+
+## Pattern.addPart() example
+
+```js
+import { Aaron } from "@freesewing/aaron"
+
+const extra = {
+  name: 'aaron.extra',
+  draft: ({ points, Point, paths, Path, part }) => {
+    points.msg = new Point(50,15)
+      .attr('data-text', "I am an extra part")
+    paths.box = new Path()
+      .move(new Point(0,0))
+      .line(new Point(0,30))
+      .line(new Point(100,30))
+      .line(new Point(100,0))
+      .close(new Point(100,0))
+      .addClass('note')
+
+    return part
+  }
+}
+
+// Load some public test measurements from the FreeSewing backend
+const measurements = (
+  await (
+    await fetch("https://backend3.freesewing.org/curated-sets/1.json")
+  ).json()
+).measurements
+
+const pattern = new Aaron({ measurements }).addPart(extra)
+
+const svg = pattern.draft().render()
+```