Release v1.5.6

Changes since v1.4.160:

• Engine: add support for "language packs" - .po files placed right next to
  the game executable.
• Engine: update dependencies.
• Level: add a very obscure easter egg (not required for any run).
• Level: minor change to the "Dopefish Lives" section (improves flow, but may
  break existing TAS runs for 100%, but same times definitely are achievable).
• Menu: show something about the number of question blocks hit.
• Translations: add Arabic and Arabic (Egypt). Thank you,
  Mo'taz Elhag (معتز الحاج)!