Adds code formatting to contributing guidelines

[andresgalante]

Hi, this is a small change, it just adds a bit of formatting to the contribution guidelines

[codecov]

Codecov Report

Merging #6119 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6119      +/-   ##
==========================================
- Coverage   93.75%   93.73%   -0.03%     
==========================================
  Files         165      165              
  Lines       11199    11199              
==========================================
- Hits        10500    10497       -3     
- Misses        699      702       +3

Impacted Files	Coverage Δ
src/Routers/PushRouter.js	93.1% <0%> (-3.45%)	⬇️
src/Adapters/Storage/Mongo/MongoStorageAdapter.js	92.27% <0%> (-0.71%)	⬇️
src/RestWrite.js	93.56% <0%> (+0.16%)	⬆️

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