feat: TS type information for remark-stringify and remark-parse

[mike-north]

This pull request adds typescript ambient type information for the remark-stringify package, as well as acceptance tests for types that's run in CI as a second Travis-CI stage

This change enables things TypeScript consumers to do things like this

import * as remarkStringify from 'remark-stringify'
/*
 * 👇 "ghost module" containing only type information, to avoid risk of colliding
 * w/ anything in a value-exporting module 
 */
import {RemarkStringifyOptions} from 'remark-stringify/types'
import * as unified from 'unified'

/** 
 * 👇 type-checking on the options object, including string literal types
 * for things like `fence`, `bullet`, etc...
 */
const stringifyOptions: Partial<RemarkStringifyOptions> = {
  gfm: true,
  bullet: '*',
  fences: true,
  fence: '`',
  incrementListMarker: false
}

unified().use(remarkStringify, stringifyOptions)

[Rokt33r]

Check the prior works in unified ecosystem. vfile/vfile#33

And please update https://github.com/remarkjs/remark/blob/master/package.json too.

• Update format script for prettier to format .ts files also.

packages/remark-cli/cli.js . -qfo && prettier --write '**/*.{js,ts}' && xo --fix

• Add test-types script to test types of each package via lerna.
• Append npm run test-types to test script.

BTW, thanks for the contribution! 😄

[Rokt33r]

@wooorm I reviewed it again. It looks good to me now.

The only problem is how should we deploy this. The change will force adopters to use typescript v3.2 or above. So I think we should increase major version.

[wooorm]

Perfect! Yes, remark is about to be updated with a major version, so that’s fine!

[wooorm]

Does remark itself need types?

[ChristianMurphy]

Does remark itself need types?

@wooorm good call, remark itself also has types in the latest updates to this PR