Add docs for cherry pick workflow on RELEASE.md

[ffjlabo]

What this PR does / why we need it:

as title

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[Warashi]

🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 22.84%. Comparing base (c24ce35) to head (3e6aa30).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5158      +/-   ##
==========================================
+ Coverage   22.82%   22.84%   +0.02%     
==========================================
  Files         412      412              
  Lines       43833    43833              
==========================================
+ Hits        10003    10013      +10     
+ Misses      33040    33031       -9     
+ Partials      790      789       -1     

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