Added weeks to afrikaans locale

[oestej]

Pull Request Checklist

Thank you for taking the time to improve Arrow! Before submitting your pull request, please check all appropriate boxes:

• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
• 🧹 All linting checks pass when run locally (run tox -e lint or make lint to find out!).
• 📚 Updated documentation for changed code. (N/A, fixes a crash for week/weeks when using the Afrikaans locale for humanization)
• ⏩ Code is up-to-date with the master branch.

If you have any questions about your code changes or any of the points above, please submit your questions along with the pull request and we will try our best to help!

Description of Changes

Adds week and weeks translations for Afrikaans, adds very basic tests for Afrikaans

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (master@2c1f518). Learn more about missing BASE report.
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##             master     #1234   +/-   ##
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  Coverage          ?   100.00%           
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  Files             ?        10           
  Lines             ?      2315           
  Branches          ?       358           
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  Hits              ?      2315           
  Misses            ?         0           
  Partials          ?         0           

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[jadchaar]

LGTM, but mind removing junit.xml? It was mistakenly pushed and has since been removed and added to gitignore. Updating branch now causes merge conflicts.

[oestej]

Done