doc: GitHub PRs workflow

[catenacyber]

Link to redmine ticket:
None

Describe changes:

• adds a documentation about GitHub PRs workflow

Draft : to be discussed, and to see if the approved filter with gh command is good enough ?

Modifies #8925 by taking review into account

[jufajardini]

Ok, I ran one last picky review, and submitted everything as suggestions, so, if you want, we can try to commit these and see if this version can be merged (IMO).

[codecov]

Codecov Report

Merging #8926 (5dd4b2f) into master (ebe0a7b) will increase coverage by 0.04%.
The diff coverage is n/a.

❗ Current head 5dd4b2f differs from pull request most recent head 5efb041. Consider uploading reports for the commit 5efb041 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8926      +/-   ##
==========================================
+ Coverage   82.30%   82.34%   +0.04%     
==========================================
  Files         969      969              
  Lines      273335   273336       +1     
==========================================
+ Hits       224961   225075     +114     
+ Misses      48374    48261     -113     

Flag	Coverage Δ
fuzzcorpus	64.75% <ø> (+0.10%)	⬆️
suricata-verify	60.44% <ø> (-0.02%)	⬇️
unittests	62.95% <ø> (+<0.01%)	⬆️

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[catenacyber]

Replaced by #8946