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/packages/snapseries/readme.mdx

@@ -0,0 +1,61 @@
+---
+title: snapseries
+---
+
+Published as [@freesewing/snapseries][1], this package provides series
+of common sizes for elastics and zippers and series of common intervals
+to be used with snapped percentage options.
+
+## Exports
+
+All exports are plain objects with `metric` and `imperial` properties
+that can be used as the `snap` property for snapped percentage options.
+
+Some exports have `metric` and `imperial` properties that are
+arrays of numbers.
+These exports and their properties are:
+
+- `elastics`: Arrays of common elastic widths
+- `zippers`: Arrays of common zipper lengths
+
+Other exports have `metric` and `imperial` properties that are
+numbers to allow options to be _snapped_ to multiples of the value.
+These exports and properties are:
+
+- `smallSteps`: Intervals of 1 mm or 1/32 inch
+- `steps`: Intervals of 5 mm or 1/8 inch
+- `bigSteps`: Intervals of 10 mm or 1/2 inch
+
+## Installation
+
+```sh
+npm install @freesewing/snapseries
+```
+
+## Example
+
+In NodeJS:
+```js
+import { elastics } from @freesewing/snapseries
+
+myOption: {
+  pct: 10,
+  min: 5
+  max: 35,
+  snap: elasitcs,
+}
+```
+
+## Units
+
+All measurements are in mm.
+
+:::note RELATED
+
+Please see
+[Snapped percentage options](/reference/api/part/config/options/pct/snap)
+to learn more about how snapped percentage options are used.
+
+:::
+
+[1]: https://www.npmjs.com/package/@freesewing/snapseries