[Devtools Week] Update contributing guide

[thepetk]

Please specify the area for this PR

/registry-support

What does does this PR do / why we need it:

This PR updates the registry-support contributing guide to align it with the discussion made for the updates of the alizer contributing guide: devfile/alizer#39

Which issue(s) this PR fixes:

fixes devfile/api#1348

PR acceptance criteria:

• Test Coverage
  • Are your changes sufficiently tested, and are any applicable test cases added or updated to cover your changes?

Documentation (WIP)

• Does the REST API doc need to be updated with your changes?
• Does the registry library doc need to be updated with your changes?

How to test changes / Special notes to the reviewer:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (321dced) 35.58% compared to head (405a715) 35.58%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #194   +/-   ##
=======================================
  Coverage   35.58%   35.58%           
=======================================
  Files           7        7           
  Lines        1360     1360           
=======================================
  Hits          484      484           
  Misses        829      829           
  Partials       47       47           

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[michael-valdron]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: michael-valdron, thepetk

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