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/path/intersectsy/readme.mdx

@@ -0,0 +1,58 @@
+---
+title: Path.intersectsY()
+---
+
+The `Path.intersectsY()` method returns the Point object(s) where the path
+intersects with a given Y-value.
+
+:::warning
+
+This method can sometimes fail to find intersections in some curves
+due to a limitation in an underlying Bézier library.
+Please see [Bug #3367](https://github.com/freesewing/freesewing/issues/3367)
+for more information.
+
+:::
+
+## Signature
+
+```js
+array|false path.intersectsY(float y)
+```
+
+## Example
+
+<Example caption="Example of the Path.intersectsY() method">
+```js
+({ Point, points, Path, paths, snippets, Snippet, getId,  part }) => {
+
+    points.A = new Point(55, 40)
+    points.B = new Point(10, 70)
+    points.BCp2 = new Point(40, 20)
+    points.C = new Point(90, 60)
+    points.CCp1 = new Point(50, -30)
+    points.D = new Point(50, 80)
+    points.DCp1 = new Point(140, 50)
+
+    points.top = new Point(10, 58)
+    points.bot = new Point(130, 58)
+
+    paths.line = new Path()
+    .move(points.top)
+    .line(points.bot)
+    .attr("class", "lining dashed")
+
+  paths.demo = new Path()
+    .move(points.A)
+    .line(points.B)
+    .curve(points.BCp2, points.CCp1, points.C)
+    .curve(points.DCp1, points.DCp1, points.D)
+
+  for (let p of paths.demo.intersectsY(58)) {
+    snippets[getId()] = new Snippet("notch", p)
+  }
+
+  return part
+}
+```
+</Example>