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/macros/ringsector/readme.mdx

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+---
+title: ringSector
+---
+
+The `ringsector` macro drafts a ring sector, which is like a part of a donut
+with an inside and outside radius. It is particularly useful for drafting
+curved waistbands, circle skirts, and so on.
+
+It is provided by the [ringsector plugin](/reference/plugins/ringsector).
+
+:::note
+##### Not a core-plugins macro
+
+The `ringsector` macro is not provided by the [core-plugins](/reference/plugins/core),
+so you need to load the [ringsector plugin](/reference/plugins/ringsector) explicitly
+if you want to use it.
+:::
+
+## Signature
+
+```js
+macro('ringsector', {
+  String id='ringsector',
+  Point center = new Point(0,0),
+  Number angle,
+  Number insideRadius,
+  Number outsideRadius,
+  Boolean rotate = false,
+})
+```
+
+## Example
+
+<Example caption="Example of a ring sector drafted by this macro">
+```js
+({ Point, macro, Path, paths, part }) => {
+
+  macro('ringsector', {
+    angle: 60,
+    insideRadius: 30,
+    outsideRadius: 45,
+  })
+
+  return part
+}
+```
+</Example>
+
+## Configuration
+
+| Property       | Default           | Type                | Description |
+|---------------:|-------------------|------------|-------------|
+| `id`           | `ringsector`      | String     | The id to use in auto-generate macro points and paths |
+| `center`       | `new Point(0,0)`  | [Point][1] | The center point of the ring sector |
+| `angle`        |                   | Number     | The angle the ring sector should cover |
+| `insideRadius` |                   | Number     | The inside radius of the ring sector |
+| `outsideRadius` |                  | Number     | The outside radius of the ring sector |
+| `rotate`       | `false`           | Boolean    | Whether or not to rotate the ringsector so one of its sides is vertical (see [example below](#example-when-rotatetrue)) |
+
+[1]: /reference/api/point
+
+## Notes
+
+The `ringsector` macro creates a `path` that can be used as a seam path for a part. If doing so, the left side of the path assumes a `cutOnFold`, as the `sa` is not offset here like it is along the rest of the `path`.
+
+### Example when rotate=true
+
+<Example caption="Example of a ring sector drafted by this macro when rotate is truthy">
+```js
+({ Point, macro, Path, paths, part }) => {
+
+  macro('ringsector', {
+    angle: 60,
+    insideRadius: 30,
+    outsideRadius: 45,
+    rotate: true,
+  })
+
+  return part
+}
+```
+</Example>
+