ci: swap nyc with c8 for unit test coverage reports

[radomir-sebek]

Two improvements come with this PR:

1. swapping nyc to c8

• When trying to calculate coverage with nyc, I am always getting 0% with existing scripts/tooling. It seems that nyc (Istanbul) was originally designed for CommonJS, and its code instrumentation hooks into the require system. By looking at test/*.test.js I can see code instrumented as ESM (with import ... from ...), so it NYC cannot instrument source files, at least not right away so I would need to use additional loader or similar.
• Internet tells me that c8 works natively with ESM and its recommended for ESM projects.

before:

after:

2. added html reporter and exposed calculated artefacts so they can be accessible also on demand

PS. If there is ever desired to require minimum coverage threshold, one can set check-coverage to true and "demand" /instrument line coverage, or any of (functions, statements, branches) to not go bellow specified threshold. For now, its disabled.

  "check-coverage": false,
    "lines": 80 , 

[Bojan131]

This looks great i really like it. We can talk about expanding these to other repos on the QA Guild. Lets wait for Mihajlo to also take a look and approve if everything is ok on his side

[radomir-sebek]

This looks great i really like it. We can talk about expanding these to other repos on the QA Guild. Lets wait for Mihajlo to also take a look and approve if everything is ok on his side

Thank you, sure, lets see if @Mihajlo-Pavlovic gives thumbs up here, I would love to merge it soon :)