chore: Slovak translation, enabling language and adding first translations

[minho95]

SUMMARY

Adding first translations for the Slovak language.

[codecov]

Codecov Report

Merging #14783 (2e4fd66) into master (69f9ee8) will increase coverage by 0.04%.
The diff coverage is 84.38%.

❗ Current head 2e4fd66 differs from pull request most recent head 00bcf7e. Consider uploading reports for the commit 00bcf7e to get more accurate results

@@            Coverage Diff             @@
##           master   #14783      +/-   ##
==========================================
+ Coverage   76.96%   77.00%   +0.04%     
==========================================
  Files        1043     1048       +5     
  Lines       56376    56514     +138     
  Branches     7797     7805       +8     
==========================================
+ Hits        43388    43518     +130     
- Misses      12732    12742      +10     
+ Partials      256      254       -2     

Flag	Coverage Δ
hive	81.57% <87.85%> (+0.03%)	⬆️
mysql	81.99% <88.13%> (+0.03%)	⬆️
postgres	82.00% <88.13%> (+0.03%)	⬆️
presto	81.87% <87.85%> (+0.04%)	⬆️
python	82.50% <88.13%> (+0.04%)	⬆️
sqlite	81.68% <87.85%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...erset-frontend/src/SqlLab/components/App/index.jsx	56.66% <ø> (ø)
...frontend/src/SqlLab/components/ResultSet/index.tsx	61.48% <ø> (ø)
...t-frontend/src/dashboard/actions/dashboardState.js	28.80% <0.00%> (-0.16%)	⬇️
...board/components/nativeFilters/FilterBar/index.tsx	88.18% <ø> (ø)
superset-frontend/src/views/CRUD/hooks.ts	52.76% <0.00%> (ø)
...d/src/visualizations/TimeTable/FormattedNumber.tsx	0.00% <0.00%> (ø)
superset/config.py	91.53% <ø> (ø)
superset/databases/commands/exceptions.py	94.00% <ø> (ø)
.../src/views/CRUD/alert/components/RecipientIcon.tsx	60.86% <20.00%> (ø)
...rc/views/CRUD/alert/components/AlertStatusIcon.tsx	46.96% <31.25%> (ø)
... and 39 more

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[villebro]

Thanks so much for the contribution @minho95 and sorry for not getting to this PR sooner 🙁 I rebased the PR and fixed the conflict and will merge when CI passes.

[minho95]

Thank you for your approval @villebro. Is there something I can do to fix E2E testing?

[villebro]

@minho95 it seems to be a flaky test, and should sort itself out (I've restarted the job). However, I notice there is no .json translation file, only the .po file. Can you check if you've followed all steps as outlined here: https://github.com/apache/superset/blob/master/CONTRIBUTING.md#updating-language-files