Add patch for 1.21.2

Bug: 55640
Change-Id: I04bd4398daf31d2f07825db17819e6654a8f3466
Update README

More general source url and updated preferences url

Change-Id: I92f2ff8796bb9650931ef11e133d36e25a1bfe9d
Migrate to JSON i18n

Procedure per https://www.mediawiki.org/wiki/Manual:GenerateJsonI18n.php
with shim.

Change-Id: I659c68791e7ce1189d846429086a7e966b2049db