Updated mediawiki/extensions
Project: mediawiki/extensions/Translate  58971d9a94af27f156c46340bd41e9e7168cbdff
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Intialise possible unset variables and add type hints

Also: A few typos in docs fixed.

Change-Id: I54309d4e9d4d0f7e91a9e5896a1c68a1006e3442