request: better SeekBarPreference

[adrcotfas]

Hi Gericop,

Something like this would be very nice to have: https://github.com/MrBIMC/MaterialSeekBarPreference which unfortunately doesn't seem to be updated anymore. Edit: Or something like this: https://github.com/AnderWeb/discreteSeekBar

Differences from the default SeekBarPreference:

• the summary to the right is updated while dragging, not on release
• a unit of measurement can be provided in the summary to the right (plurals support depending on value: 1 banana / 10 bananas)
• the summary to the right can be clicked to show a dialog identical to the dialog of an EditTextPreference; this is used to update the seekbar with a precise value