[REQUEST] Support for user/system themes directory

[sitiom]

Is your feature request related to a problem? Please describe. Support for a user or system themes directory for custom themes.

Describe the solution you'd like

The Windows agnostic locations of these folders would be:

User directory in %appdata%\btop System directory in %programdata%\btop

Describe alternatives you've considered

Additional context Related with Scoop persistence (https://github.com/ScoopInstaller/Main/pull/3897). This is needed as Scoop will keep persisting old version of themes if they get updated on a newer version.

[Firehawke]

I'd be fine with ~.config\btop for the user directory. I've got several other tools now using ~.config even on Windows.