add y as year abbreviation

[noviluni]

Fixes #516

[codecov]

Codecov Report

Merging #562 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #562   +/-   ##
=======================================
  Coverage   95.06%   95.06%           
=======================================
  Files         302      302           
  Lines        2492     2492           
=======================================
  Hits         2369     2369           
  Misses        123      123

Impacted Files	Coverage Δ
dateparser/data/date_translation_data/en.py	100% <ø> (ø)	⬆️

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[codecov]

Codecov Report

Merging #562 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
+ Coverage   95.04%   95.06%   +0.02%     
==========================================
  Files         302      302              
  Lines        2481     2492      +11     
==========================================
+ Hits         2358     2369      +11     
  Misses        123      123

Impacted Files	Coverage Δ
dateparser/data/date_translation_data/en.py	100% <ø> (ø)	⬆️
dateparser/utils/strptime.py	100% <0%> (ø)	⬆️

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[asadurski]

So far you added translation tests (good!). What would also be required are the tests for parsing functionality (suggestions, here: https://github.com/scrapinghub/dateparser/blob/master/tests/test_date_parser.py#L29 and here: https://github.com/scrapinghub/dateparser/blob/master/tests/test_freshness_date_parser.py#L34).
What I usually do is add exactly the cases from the issue which is closed by the PR (e.g. the cases mentioned in #516 (comment)).