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/pctbasedon/readme.mdx

@@ -0,0 +1,35 @@
+---
+title: utils.pctBasedOn()
+---
+
+The `utils.pctBasedOn()` function is a helper function to be used when
+configuring [snapped percentage
+options](/reference/api/part/config/options/pct/snap). 
+
+
+## Signature
+
+```js
+object utils.pctBasedOn(String measurement)
+```
+
+## Example
+
+```js
+const options = {
+  example: {
+    pct: 12,
+    min: 5,
+    max: 18,
+    snap: 3,
+    ...pctBasedOn('chest')
+  }
+}
+```
+
+## Notes
+
+This will return an object with `toAbs` and `fromAbs` properties that calculate
+the option's absolute and relative values based on a measurement. Refer to
+[snapped percentage options](/reference/api/part/config/options/pct/snap) for
+more details.