Use submodules to maintain a long-term fork of Overtype

[nedtwigg]

Overtype is designed for creating new text areas, it is currently pretty awkward for modifying existing text areas. Hopefully we can eventually prepare a succinct PR that the upstream project will be willing to merge, but in the meantime we will need to maintain a fork for a while.

• the fork lives in packages/overtype and is hosted at https://github.com/diffplug/overtype
• it's currently just the upstream main, plus we ignored dist, plus we merged feat: support codeblock syntax highlighting panphora/overtype#35
• closes make the overtype fork long-term sustainable #27

[nedtwigg]

@WebsByTodd this is ready! If you check it out and run pnpm run har:view in the root directory, then you'll have a development environment where you can

• edit our extension or overtype
• hit the refresh in the top right
• it will build both things

I'm not merging this PR because things are overall worse, specifically styles.js. But other things are better - links and bullets are both much better.

Once you get a chance to bring this PR up to parity with main then we can merge this.

[nedtwigg]

Oh! Also, I tried to use "npm workspaces", I did not want to switch to pnpm. But workspaces has bugs / missing features related to platform-specific stuff. So developing on Mac Silicon and running CI on linux was bad. I fixed/worked-around one issue, and then hit another one. That was when I switched to pnpm, which just worked. So that's how we got stuck with pnpm.

[WebsByTodd]

• Also fixes italics play nicely with asterisk but not underscore #3