Fixed Custom width and height lightbox
Grid image overlays fix for mobile

Grid image overlays are controlled through animations - but those animations don't happen on mobile because they are triggered via hover - which isn't a thing on touch devices. This sets the overlay to be in the state it would be when the mouse is hovered all the time
Add Knapstack to the Themes page if not installed

MP Stacks buddy theme "Knapstack" should be easily available to all user of MP Stacks - so we put a pseudo version under "Appearance" > "Themes" if the user doesn't have it installed on their WordPress so it is easy and handy to install with a click.