Feat/codecov

[jackey8616]

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you written unit tests?
• Have you written unit tests that cover the negative cases (i.e.: if bad data is submitted, does the library respond properly)?
• This PR is associated with an existing issue?

Closing issues
Closes #836, #840

Details code coverage report can check my forked repo's actions output.

[jackey8616]

@WoH Can you re-run the failed job? Thx.
Actions in my repo is all passed.

[jackey8616]

@WoH I'm still trying to work on middleware & file decorator.
But currently I think everything is all set for code coverage.

[WoH]

I hope that this does not mess around too much with lerna and ts, but only one way to know for sure :D

[jackey8616]

@WoH I've noticed that I missed esm tests cases while I was resolving conflicts in #1540 & #1541,
Could you revert this PR & re-open it?

After I resolve 1540 & 1541, and fix this pr, then I will ask for your review?