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/utils/beamintersectsx/readme.mdx

@@ -0,0 +1,40 @@
+---
+title: utils.beamIntersectsX()
+---
+
+The `utils.beamIntersectsX()` function finds the intersection between an endless
+line and a given X-value. Returns a [Point](/reference/api/point) object for
+the intersection, or `false` there is no intersection.
+
+## Signature
+
+```js
+Point | false utils.beamIntersectsX(Point A, Point B, float X)
+```
+
+## Example
+
+<Example caption="A Utils.beamIntersectsX() example">
+```js
+({ Point, points, Path, paths, Snippet, snippets, utils, part }) => {
+
+  points.A = new Point(10, 10)
+  points.B = new Point(90, 30)
+
+  paths.AB = new Path().move(points.A).line(points.B)
+
+  snippets.x = new Snippet(
+    "notch", 
+    utils.beamIntersectsX(points.A, points.B, 40)
+  )
+
+  paths.help = new Path()
+    .move(new Point(40, 5))
+    .line(new Point(40, 35))
+    .addClass("note dashed")
+
+  return part
+}
+```
+</Example>
+