Some things I think should be added to the docs

[code-IM-perfect]

The current documentation is great but I think it currently skips over some important getting started things, it relies a bit too much on looking at other people's configs to figure those things out.

These are some of the things I think should be added:

• The recommended way to theme in a modular way
• create popups for the widgets, especially for the bar (the recommended way)
• handling mouse input (particularly for scroll up/down, useful for example in volume widgets)
• Debugging the various Quickshell modules, particularly the models where you're not sure what an object's property would be, like I use console.log(JSON.stringify(<the_model_or_whatever>, null, "\t")) every time I want to get an overview of whatever I'm working with.
• Animations (please)
• Maybe a bit to setup the System Tray, I struggled a bit to get it working, but that's not really necessary.

I understand that most of the documentation that should be referred in using quickshell is for qml itself, but I believe these particular things should be added to quickshell's config itself.