Add SchildiChat to clients (#301)

* Add SchildiChat to clients

mostly adapted version of element.js,
as SchildiChat is an fork of Element.

* SchildiChat: Change description to new official one

Reason: https://github.com/matrix-org/matrix.to/pull/301#issuecomment-1465739125
Source: https://raw.githubusercontent.com/SchildiChat/SchildiChat-android/5bbd462cdbecf64ceda7e65e8cd8a4e241bfca03/fastlane/metadata/android/en-US/short_description.txt

* SchildiChat: Add test instance to trusted web instances

Reason: https://github.com/matrix-org/matrix.to/pull/301#issuecomment-1465739125