Fixed custom style to be within Qt6 requirements (qmldir)

[chinese-soup]

Aaaand we're back...

This took way too much time to get properly working, stupid qrc and paths and other bullshit, ugh. :|

I've also added some more changes to stuff like events to get rid of new qt6 warnings like these:

QML Connections: Implicitly defined onFoo properties in Connections are deprecated. 
Use this syntax instead: function onFoo(<arguments>) { ... }

qt.qml.context: qrc:/ChannelMessage.qml:56:9 Parameter "mouse" is not declared. 
Injection of parameters into signal handlers is deprecated. Use JavaScript functions with formal parameters instead.

[MartinBriza]

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