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/attributes/clone/readme.mdx

@@ -0,0 +1,23 @@
+---
+title: Attributes.clone()
+---
+
+The `Attributes.clone()` method returns a new Attributes object that is a deep
+copy of this one.
+
+## Signature
+
+```js
+Attributes attributes.clone()
+```
+
+## Example
+
+```js
+const attr = new Attributes()
+  .add('class', 'classA')
+  .add('class', 'classB')
+
+const cloned = attr.clone()
+```
+