Update CONTRIBUTING.md

[tsuwandy]

Add step to update rush.json

[codecov-commenter]

Codecov Report

Merging #873 into master will decrease coverage by 0.72%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #873      +/-   ##
==========================================
- Coverage   57.87%   57.14%   -0.73%     
==========================================
  Files         213      213              
  Lines       15223    14947     -276     
  Branches     2047     2077      +30     
==========================================
- Hits         8810     8542     -268     
+ Misses       5875     5847      -28     
- Partials      538      558      +20     

Impacted Files	Coverage Δ
...kages/luis/src/commands/luis/application/create.ts	61.11% <0.00%> (-19.85%)	⬇️
...rc/commands/luis/application/assignazureaccount.ts	82.60% <0.00%> (-17.40%)	⬇️
packages/command/src/clierror.ts	50.00% <0.00%> (-16.67%)	⬇️
packages/qnamaker/src/commands/qnamaker/index.ts	66.66% <0.00%> (-16.67%)	⬇️
...ackages/luis/src/commands/luis/application/list.ts	84.61% <0.00%> (-15.39%)	⬇️
...ematics/mathematics_helper/AppMathematicsHelper.ts	85.71% <0.00%> (-14.29%)	⬇️
...atics/confusion_matrix/AppBinaryConfusionMatrix.ts	85.71% <0.00%> (-14.29%)	⬇️
...ckages/luis/src/commands/luis/application/query.ts	73.33% <0.00%> (-14.17%)	⬇️
...ages/luis/src/commands/luis/application/publish.ts	87.50% <0.00%> (-12.50%)	⬇️
...kages/luis/src/commands/luis/application/import.ts	54.34% <0.00%> (-11.28%)	⬇️
... and 117 more

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