Also update targetSDKVersion to 30

chore(android): Update targetSDKVersion to 30

To comply with upcoming Play Store requirement, this updates targetSDKVersion to 30.

* Also sets appropriate webView permissions to access local file (except for WebBrowserActivity, the in-app browser).

chore(mac): Add help links for installing Keyman and keyboards

chore(ios): update fv cert ref

chore(web): add test page for playing with CKEditor

chore(android): Update Gradle and other dependencies

fix(developer): TframeTextEditor.SetText was not synchronous

feat(developer): Add 'full copyright' field to templates

chore(windows): reorganise tests

auto: increment master version to 15.0.51

chore(linux): Remove unnecessary dependency on kmflcomp

chore(linux): Swap order of dependency

refactor(linux): Refactor `install_kmp.py`

chore(common): resolve audit issues in Web-related repo NPM packages

chore(common): Check in crowdin strings for Amharic

auto: increment master version to 15.0.50

This was already partially done in 4dd0a48b, but we missed this
line.

Closes #4768.

fix(common/core/desktop): Don't segfault on invalid .kmx file

fix(common/core/desktop): Fix warnings when compiling for armhf

refactor(linux): Remove obsolete SCIM kmfl imengine

(Fixes #5100)

Compiling on armhf outputs two warnings:
- NULL used in arithmetic [-Wpointer-arith] (line 289 and 290)
- unused parameter ‘dwFileSize’ [-Wunused-parameter] (line 264)

(related to #5072)