Long pressing will change the value by 1000, whereas clicks will change
it by 500. This allows setting more precise values, while also making it
easier to set any value.
value_str is a way to add text on a button without a separate label.
This saves having an extra label object, but uses more memory and is
removed in LVGL8
Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.
