[draft] Update all deps

[mrienstra]

Major changes:

• Parcel v1 --> v2: https://parceljs.org/getting-started/migration/
• TypeScript v3 --> v4: https://github.com/microsoft/TypeScript/wiki/Breaking-Changes
• @actions/github v4 --> v5
• babel-jest v24 --> v29
• fs-extra v8 --> v10
• husky 3 --> 8
• jest 24 --> 29
• mdast-util-to-string v1 --> v3
• remark-parse v7 --> v10
• remark-stringify v7 --> v10
• semver v6 --> v7
• unified v8 --> v10

Got stuck trying to fix SyntaxError: Unexpected token 'export' when running yarn test, this seems to be coming from the unified import in src/utils.ts.

I tried using @babel/plugin-transform-modules-commonjs with option importInterop: "none", tried switching to ts-jest, & tried transformIgnorePatterns... And a few more things that I didn't document.

If anyone wants to pick this up and give it a whirl, that would be great! Also open to suggestions on how to proceed.

[changeset-bot]

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Latest commit: 7fad5e4

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[Andarist]

Some of those updates might be a little problematic - while other ones might be mergeable immediately. For that reason, I would recommend splitting this into multiple PRs.