Add stale bot

[diegomarangoni]

What this PR changes:

EES-4232

• This PR adds a stale bot to the repository

[codecov]

Codecov Report

Merging #127 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #127   +/-   ##
=======================================
  Coverage   41.54%   41.54%           
=======================================
  Files           8        8           
  Lines         284      284           
=======================================
  Hits          118      118           
  Misses        159      159           
  Partials        7        7           

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[s4nji]

+1