MediaCategoryViewController: Fix the Continue Watching button's constraints
This merge request brings a fix to the continue watching button with:
- Both the regular tab bar and the custom tab bar (made for iPads) heights that are now taken into consideration when the button's bottom constraint padding is computed
- The continue watching button that now has a background layer that creates a shadow
This prevents:
- The button from overlapping with the tab bar at the bottom especially on iPad devices
- It makes the button stand out from the content it is currently covering especially when the bright theme is selected