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/howtos/code/create-new-design/readme.mdx

@@ -0,0 +1,40 @@
+---
+title: Creating a new design
+---
+
+When creating a new design, you have two options. You can create it in a
+stand-alone development environment. Or, you can create it inside (your fork of)
+the FreeSewing monorepo.
+
+If you are unsure what to pick, go with the stand-alone development environment.
+It is the best choice for people new to FreeSewing.
+
+Working inside the monorepo is the preferred way of regular contributors, but
+if you were a regular contributor, you would probably already know this. So
+when in doubt, go stand-alone. You can always change track later.
+
+## Stand-alone
+
+To setup the stand-alone development environment, you need NodeJS 18 or higher.
+Then run:
+
+```sh
+npx @freesewing/new-design
+```
+
+This command will setup FreeSewing's stand-alone development environment.
+
+## Work inside the monorepo
+
+First, [fork our monorepo](https://github.com/freesewing/freesewing/fork). Then run:
+
+```sh
+git clone <url to your fork>
+cd freesewing
+yarn kickstart
+yarn new design
+```
+
+These commands will clone your fork of the
+[freesewing/freesewing](https://github.com/freesewing/freesewing) repository on
+GitHub and set it up for development.