Support TypeScript Node16/NodeNext module resolution

[robwalch]

This PR will...

Let TypeScript find the corresponding TypeScript definition file (.d.mts and.d.ts) by extension substitution for ESM and UMD library exports.

Why is this Pull Request needed?

This is to satisfy https://arethetypeswrong.github.io/?p=hls.js

Are there any points in the code the reviewer needs to double check?

Resolves issues:

Resolves #6612

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

[aaronadamsCA]

@robwalch, I've seen other libraries just copy the definition file, so yes, I think this approach should work.

However, you'll either need to rename the definition files without the .js in them so TypeScript can automatically resolve them, or just be explicit about the filenames:

  "exports": {
    ".": {
      "import": {
        "types": "./dist/hls.js.d.mts",
        "default": "./dist/hls.mjs"
      },
      "default": {
        "types": "./dist/hls.js.d.ts",
        "default": "./dist/hls.js"
      }
    },
    "./dist/*": "./dist/*",
    "./package.json": "./package.json"
  },

Also note you can npm pack a build and upload it to https://arethetypeswrong.github.io/ to check if the types resolve correctly before publishing any changes.

[robwalch]

I renamed the definition files, with the default output as "hls.d.ts" and the copy task creating "hls.d.mts" and "hls.js.d.ts". The last one is for backwards compatibility with direct links to the original definition file name.

[robwalch]

@aaronadamsCA

The latest changes pass all arethetypeswrong checks. Let me know if you spot anything else or if this looks good to merge.

[aaronadamsCA]

@robwalch This looks good to me! +1 to addition by subtraction.

The TypeScript 4.7 release notes confirm "types" was never necessary unless the definition files were in a different location, so as far as I can see this change shouldn't introduce any new problems.