Copy supported languages from judge-server to README

[int-y1]

Changes to the README:

• Whitespace cleanup
• Copy+paste supported languages from judge-server. This mostly affects Java.

[quantum5]

Otherwise seems okay.

[codecov-commenter]

Codecov Report

Merging #1792 (984f9f2) into master (0458b06) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1792   +/-   ##
=======================================
  Coverage   46.19%   46.19%           
=======================================
  Files         223      223           
  Lines       12678    12678           
=======================================
  Hits         5857     5857           
  Misses       6821     6821           

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