Fresh 1.6.8

Fixes: #38.

Without this, the checkboxes would not be rendered correctly.
They weren't checked when the user clicked on them.
This was due to another annoying csp violation.
Oversight on my part.
I apologize, I hope this is the last time I have to fix this.

54 characters removed, for a total of a 50 line reduction of code!

Bump preact.
Downgrade gfm to a csr compatible version.

HeadlessUI v2.0 is broken, and HeadlessUI v1.18 added code from v2.0.
It's mostly turned off, but it's still in the bundle.
It relies on process.env.JEST_WORKER_ID to disable some features.
We use combobox, the affected component, so we can't upgrade.

I disabled some rules:
useDefaultSwitchClause doesn't have type information.

It found a real bug in compile-mdx.
Luckily, JS was lenient enough it didn't make a big deal.

The csp didn't work right with latest fresh.

Apparently f-client-nav requires the direct child to be a partial.
It works fine otherwise, so I hadn't noticed.
However, it turns out `f-client-nav`ed islands must be partialled.

I gave up on streaming for now, but this is still a nice simplification.

Upgrade Dependencies

Fix Homepage Dark Mode

Refactor Path Resolution Logic in MDX Compilation File Discovery

Remove ~Code

Fix Missing Partial Island Warning

Fix CSP