Added pl translation.

[turbofart]

Added new language strings for Polish (pl) language.

[codecov-io]

Current coverage is 82.66%

Merging #1518 into master will decrease coverage by -0.01% as of eb1c40b

@@            master   #1518   diff @@
======================================
  Files           79      79       
  Stmts         6108    6108       
  Branches         0       0       
  Methods          0       0       
======================================
- Hit           5050    5049     -1
  Partial          0       0       
- Missed        1058    1059     +1

Review entire Coverage Diff as of eb1c40b

---

Uncovered Suggestions

1. +0.19% via .../js/profileeditor.js#324...335
2. +0.18% via .../js/profileeditor.js#269...279
3. +0.16% via .../report/js/report.js#259...268
4. See 7 more...

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