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/shiftalong/readme.mdx

@@ -0,0 +1,55 @@
+---
+title: Path.shiftAlong()
+---
+
+The `Path.shiftAlong()` method returns a point that lies at distance travelled
+along the path.
+
+## Signature
+
+```js
+Point path.shiftAlong(float distance, int stepsPerMm = 10)
+```
+
+The second parameter controls the precision by which the path will be _walked_.
+By default, we'll divide it into 10 steps per mm.
+
+If you don't need that precision, you can pass a lower number.
+If you need more precision, you can pass a higher number.
+For most cases, the default will be fine.
+
+## Example
+
+<Example caption="Example of the Path.shiftAlong() method">
+```js
+({ Point, points, Path, paths, Snippet, snippets, part }) => {
+
+  points.A = new Point(45, 60)
+  points.B = new Point(10, 30)
+  points.BCp2 = new Point(40, 20)
+  points.C = new Point(90, 30)
+  points.CCp1 = new Point(50, -30)
+
+  paths.example = new Path()
+    .move(points.A)
+    .line(points.B)
+    .curve(points.BCp2, points.CCp1, points.C)
+
+  points.x1 = paths.example
+    .shiftAlong(20)
+    .attr("data-text", "2 cm")
+    .attr("data-text-class", "center fill-note")
+    .attr("data-text-lineheight", 6)
+  points.x2 = paths.example
+    .shiftAlong(90)
+    .attr("data-text", "9 cm")
+    .attr("data-text-class", "center fill-note")
+    .attr("data-text-lineheight", 6)
+
+  snippets.x1 = new Snippet("notch", points.x1)
+  snippets.x2 = new Snippet("notch", points.x2)
+
+  return part
+}
+```
+</Example>