Allow hot reloading on the dev server

[ptgott]

When a user runs yarn start to start a local dev server, and makes a change to a docs page, they need to restart the server and wait for a built to complete in order to see the change on the dev server. Let's set up the dev server so that it automatically rebuilds the docs on changes to the source. This might be tricky, since we need to execute the prepare-files.mts script to move docs files from the content directory to a directory structure that Docusaurus recognizes.

We need to address the following issue first:

• Use a single directory tree for writing and rendering the docs #135

[ptgott]

Related:

• The local dev server does not fast refresh/hot reload when editing partials #73