fix: use GH_TOKEN if PRIVATE_TOKEN is not set

[hborawski]

What Changed

sets PRIVATE_TOKEN to GH_TOKEN when calling to all-contributors-cli if it isn't already set

Why

all-contributors-cli uses PRIVATE_TOKEN for authentication, and auto uses GH_TOKEN, to ease use with auto, users shouldn't need to set two separate environment variables to the same value
Todo:

• Add tests
• Add docs

[codecov]

Codecov Report

Merging #1446 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1446   +/-   ##
=======================================
  Coverage   80.78%   80.79%           
=======================================
  Files          58       58           
  Lines        4294     4296    +2     
  Branches      900      901    +1     
=======================================
+ Hits         3469     3471    +2     
  Misses        586      586           
  Partials      239      239           

Impacted Files	Coverage Δ
plugins/all-contributors/src/index.ts	86.02% <100.00%> (+0.15%)	⬆️

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[adierkens]

🚀 PR was released in v9.50.0 🚀