Handle en_GB and en_US in i18n

[2br-2b]

Fixes #210

Changes proposed in this pull request:

• Add support for en_GB and en_US

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.48%. Comparing base (db482bb) to head (628a76b).
Report is 62 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #222   +/-   ##
=======================================
  Coverage   99.47%   99.48%           
=======================================
  Files          11       11           
  Lines         760      771   +11     
=======================================
+ Hits          756      767   +11     
  Misses          4        4           

Flag	Coverage Δ
macos-latest	97.07% <100.00%> (+0.06%)	⬆️
ubuntu-latest	97.07% <100.00%> (+0.06%)	⬆️
windows-latest	95.42% <100.00%> (+0.46%)	⬆️

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[hugovk]

Thanks for the PR, please could you check mypy and add a test?

[2br-2b]

Sure thing! I'll do that now real quick

[hugovk]

See #230 for a followup.