Convert code base to Typescript

[connectdotz]

Changes

• Convert all codebase to Typescript
• Replaced most manually maintained duplicated type definitions with the original types (from jest and babel)
• Given that all the code bases are now TS, I replaced the Babel typescript compiler with tsc.
• Replace babel-jest with ts-test to run Jest with better type error detection.
• Removed all flow artifacts
• Upgraded eslint with prettier
• Generate index.d.ts from the ts files.
• Removed husky.

Backward compatibility

This PR does not change functionality, and I try to keep the types as backward-compatible as possible. However, there are still some breaking changes (mainly types). Therefore, mark this as "32.0.0-beta.0" to start preparing for the next major release.

Integration Testing

I have done some preliminary tests with vscode-jest and it seems to work fine. Would encourage other dependent systems to try out and let me know if there are any other unexpected issues.

[seanpoulter]

I'm curious why you chose to remove husky at the same time.

[seanpoulter]

Wow! 👏 🎉

I'm realizing I won't be able to review a diff this big in my spare time, especially with renaming the files and changes not being picked up
3a9d429#diff-4fa18de8d59e8fbce3df7e88da529ad458bbf37e526d58d30b56707ba4d0d8b6

Sorry. That's as far as I'll get. 😶‍🌫️

[connectdotz]

@seanpoulter, Thanks for taking a look. I know this is a tough PR to review, sorry. I gave up the piecemeal approach as it made the conversion much harder 😰... You already helped, thank you.🙏 It's nice to know that I am not alone on this!

I figure we will bite the bullet and do this in one PR, but we won't release it to prod (thus the 32.0.0-beta.0 version), so we can have more time to test and fix when needed. Does that sound alright?

[connectdotz]

I'm curious why you chose to remove husky at the same time.

Mainly to simplify the env and reduce maintenance overhead. Given we already have lint/CI to detect errors and prettier-write to correct them, I thought husky/lint-staged didn't really add any extra value... Besides, we didn't use them in vscode-jest and it seems to be fine.