Austrian German + dative forms added

[adbar]

see https://en.wiktionary.org/wiki/J%C3%A4nner and https://en.wiktionary.org/wiki/Feber

[codecov]

Codecov Report

Merging #348 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #348   +/-   ##
=======================================
  Coverage   97.61%   97.61%           
=======================================
  Files          20       20           
  Lines        1674     1674           
=======================================
  Hits         1634     1634           
  Misses         40       40

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[Gallaecio]

Please, see https://dateparser.readthedocs.io/en/latest/contributing.html#guidelines-for-editing-translation-data