JSXC for Nextcloud v4.3.0-beta.1

Added

• update JSXC to 4.3.0-beta.1 (changelog)
• bump Nextcloud to version 21

Fixed

• remove obsolete variable
• command DI
• multiple DI issues
• php8 type error

Misc

• use more automated DI
• align filename with class name
• add psalm
• update dependencies
• remove deprecated mock method
• refactor deprecated tests
• refactor hooks test
• fix compatibility between nc versions
• update phpunit
• fix phpunit
• fix nc version for php 8
• fix branch name
• move to github actions
• update ci badge