feat: convert module to ts

[grant]

Converts modules from JS to TS.

• Adds typescript rollup plugin (@rollup/plugin-typescript)
• Renames source and tests to *.ts
• Does not change source code contents
• Does not change Node version
• Does not configure code style beyond default style
• Ignores all TS compiler issues
• Applies TS ESLint: plugin:@typescript-eslint/recommended and @typescript-eslint/parser
• Ignores all suggested ES lint code change suggestions beyond auto-fixed changes

Can be used as an archetypal patttern for converting other packages.

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Example output

➜  ~/Documents/github/observablehq/htl git:(grant/ts) yarn lint
yarn run v1.22.19
$ eslint .
✨  Done in 1.11s.

➜  ~/Documents/github/observablehq/htl git:(grant/ts) yarn test
yarn run v1.22.19
$ mocha --experimental-specifier-resolution=node
(node:90906) ExperimentalWarning: Custom ESM Loaders is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
(node:90906) ExperimentalWarning: The Node.js specifier resolution flag is experimental. It could change or be removed at any time.

  ✔ HTML attributes are implicitly lowercased
  ✔ SVG attributes are implicitly case-corrected
  ✔ SVG foreign attributes are implicitly namespaced
  ✔ unknown SVG foreign attributes are not implicitly namespaced
  ✔ interpolating into a tag name is not allowed
  ✔ interpolating an empty string with a suffix is not allowed
  ✔ interpolating a value with an appropriate end tag into raw text is not allowed

  7 passing (54ms)

✨  Done in 1.26s.

➜  ~/Documents/github/observablehq/htl git:(grant/ts) yarn prepublishOnly
yarn run v1.22.19
$ rm -rf dist && rollup -c && git push

bundle.ts → dist/htl.js...
created dist/htl.js in 640ms

bundle.ts → dist/htl.min.js...
created dist/htl.min.js in 588ms
Everything up-to-date
✨  Done in 2.91s.