Badges in readme should link to appropriate pages, not images)

[dmitry-mukhin]

E.g. to https://pypi.org/project/pyuploadcare/

[evgkirov]

Not sure where the "tech stack" should lead to.

[rsedykh]

I assume back in the days it was https://stackshare.io/uploadcare, but I doubt we need this these days.

[evgkirov]

Similar thing with Coveralls.

Here's the page: https://coveralls.io/github/uploadcare/pyuploadcare

It seems it stopped working since the switch from Travis CI to GitHub Actions — or even before that — 4 years ago.

I can either remove this badge or create an issue on that topic.

[rsedykh]

Let's remove old stuff.

[dmitry-mukhin]

1. coverage test, ideally we need to run those and show results. let's have a separate task for this.
2. stackshare link is still relevant, can we bring this back?

@rsedykh

[evgkirov]

#247 a separate task for coverage