Pathway to getting rid of hand-crafted .d.ts files

[fgnass]

This PR addresses type-related issues discussed in #4987 and paves the way to a more type-safe codebase.

What this PR does

1. The "build:esm" script of each package now emits TypeScript declarations in dist/esm. It does this by running babel and tsc in parallel.
2. Each package.json now has a "types" field that points to dist/esm/index.d.ts 🎉
3. Each package now has its own tsconfig.json file that extends a common base. This allows us to use proper project references instead of treating everything as one big project.
4. It fixes a circular type dependency (stega.ts was in the wrong package) and adds missing types for the semaphore npm package.

What this PR does not do

This PR does not change any of the handwritten types defined in decap-cms-core. It only converts the /index.d.ts file into src/types/index.ts.

Moving forward from here

The plan is to create a follow-up PR (once the new system is in place) that will replace the handwritten public types with the internal ones. With this PR as foundation, it will also be much easier to gradually convert more and more .js files into .ts files.

I would love to hear your feedback and if you think that this is the right way to tackle this.

[eoneill]

Thanks, this will fix #7401!

One thing might be worth doing is to add an alias to each tsconfig.json, e.g.

"compilerOptions": {
  "paths": {
    "@/*": ["./src/*"]
  }

then here you can use the alias path...

import { encodeEntry } from '@/lib/stega';

Personally, I find this easier to rationalize the file structure, when importing higher up the tree. This is definitely not required, but something to consider.

Thanks again for your awesome contributions!

[fgnass]

Thanks @eoneill, I was not aware that this was causing runtime errors! I created a separate PR (#7405) to address this in isolation.

[fgnass]

Closing this in favor of #7411