[Request] Add max_layer to overlay text template

[KilianB]

If this is a feature request describe it here

Please pass a new variable max_layer to the ovelay text template renderer. It would be nice to to show a progress on the timelapse current_layer/max_layer. Additionally it might be a good idea to allow number formatting to give us the option to add padding to those values so the numbers are always aligned

Version of Octolapse

Octolapse Version: 0.4.5

OctoPrint Version: 1.9.3