Allow customizing the format of numbers in certain modules

[pluiedev]

Is your feature request related to a problem? Please describe. Currently some modules, like sys_info, formats numbers like percentages and memory usage in GB in a fixed way, and that is sometimes not ideal. Often times I'd like these numbers to have one decimal point, and it kinda frustrates me that there's currently no way to do that.

Describe the solution you'd like Perhaps we could do it like Waybar and use a format specifier? Using a Rust style syntax, we can have something like {memory_used:.2}. That might conflict with the syntax currently reserved for specifying sensors and such for temperature readouts, but we might be able to find a compromise.

Describe alternatives you've considered Aside from different format string syntaxes, I'm not sure if there's any more alternatives other than keeping the status quo.