When running in GitHub Actions, force colors on

[AndydeCleyre]

Fixes #243

Maybe the coloring can be improved from here, this is at least what I see, with this change:

[codecov[bot]]

Codecov Report

Base: 84.94% // Head: 84.94% // Increases project coverage by +0.00% :tada:

Coverage data is based on head (1f4a041) compared to base (518a0ec). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #345   +/-   ##
=======================================
  Coverage   84.94%   84.94%           
=======================================
  Files          21       21           
  Lines        1846     1847    +1     
  Branches      284      284           
=======================================
+ Hits         1568     1569    +1     
  Misses        236      236           
  Partials       42       42           

Impacted Files	Coverage Δ
ward/_terminal.py	63.02% <100.00%> (+0.07%)	:arrow_up:

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[AndydeCleyre]

I'm having second thoughts about this, as I'm now seeing some tools checking for the environment parameter FORCE_COLOR (set to, e.g. 1). So it should probably be enough to check for FORCE_COLOR here, and let Action authors set that in the action.