Migrate all packages to TypeScript

[Josh-Cena]

💥 Proposal

Our TypeScript coverage now has reached 80%+. Recent attempts:

• mdx-loader (migrate): chore(mdx-loader): migrate package to TypeScript #5347
• theme-classic (complete): refactor(theme-classic): completely migrate package to TypeScript #5459
• plugin-debug (migrate): refactor(plugin-debug): migrate package to TypeScript #5465
• preset-classic (migrate): refactor(preset-classic): migrate preset-classic to TypeScript #5579

And chores left:

• core (complete): missing theme-fallback refactor(core): convert theme-fallback to TS #6511
• ideal-image (complete): missing theme — Thanks @armano2! refactor(plugin-ideal-image): migrate package to TS #5940
• plugin-pwa (migrate): not migrated at all — Thanks @armano2! refactor(plugin-pwa): migrate package to TS #5941
• remark-plugin-npm2yarn (migrate): not easy to migrate, Remark plugin is hard to type To anyone who ever thinks about this: be prepared. It's just 80 lines, but my three attempts to migrate it all ended up in a pathetic sea of red squiggly lines. Remark plugins are born to be JS, and just let it be. Can't believe I did it for mdx-loader—that's already remarkable enough Thanks @duanwilliam! refactor(remark-plugin-npm2yarn): migrate package to TS #5931
• live-codeblock (migrate): refactor(live-codeblock): migrate package to TS #5851
• search-algolia (migrate): not migrated at all — Thanks @armano2! refactor(theme-search-algolia): migrate package to TS #5935
• cssnano-preset: refactor(cssnano-preset): migrate to TS #7440
• stylelint-copyright: refactor(stylelint-copyright): migrate to TS #7441

Migration should be done after #5612 where we can make the theme transpiled more easily, or after #5816 where we can probably make the two transpilation targets more similar.

Have you read the Contributing Guidelines on issues?

Yes

[slorber]

Awesome, thanks for your work on this ❤️