Revise workflow badge links in README.md

[ovalenti]

Make use of github badges to show the status of the current supported releases, plus a few handy links.

Preview: https://github.com/stackrox/collector/blob/ovalenti/branch-statuses/README.md

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 27.60%. Comparing base (abacfb7) to head (79749e3).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2672   +/-   ##
=======================================
  Coverage   27.60%   27.60%           
=======================================
  Files          95       95           
  Lines        5422     5422           
  Branches     2523     2523           
=======================================
  Hits         1497     1497           
  Misses       3213     3213           
  Partials      712      712           

Flag	Coverage Δ
collector-unit-tests	27.60% <ø> (ø)

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