Add support for GitHub event branch_protection_rule

[gjabouley-invn]

Description

Add support for GitHub event branch_protection_rule
Fixes #1297
Note i had a first look at GHEventPayload.java but i don't know how to fully add the payload for this event (seems it also needs a new event class)

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[bitwiseman]

@gjabouley-invn

Note i had a first look at GHEventPayload.java but i don't know how to fully add the payload for this event (seems it also needs a new event class)

Could you talk a bit more about what you mean here? Each payload gets a new nested class inside GHEventPayload. What other "new event" would be needed?

[codecov]

Codecov Report

Merging #1301 (702833e) into main (d46bca7) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main    #1301   +/-   ##
=========================================
  Coverage     77.89%   77.89%           
  Complexity     2012     2012           
=========================================
  Files           197      197           
  Lines          6219     6220    +1     
  Branches        359      359           
=========================================
+ Hits           4844     4845    +1     
  Misses         1161     1161           
  Partials        214      214           

Impacted Files	Coverage Δ
src/main/java/org/kohsuke/github/GHEvent.java	100.00% <100.00%> (ø)

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