Introducing Custom App Launch Buttons

v3.1.0

What's New:
 - Custom App Launcher buttons (closes #152)
 - App launch button for IPTV Smarters Pro (closes #249)
 - App launch button for ITVX (closes #250)
 - Apple TV Support for BBC iPlayer (closes #251)
 - App launch button for Channel 4 (closes #252)
 - App launch button for Salt TV (closes #255)
 - App launch button for Dropout (closes #256)

What's Changed:
 - Updated device support for new Firesticks (closes #225)
   - Fire TV Stick 4K 2nd Gen (2023)
   - Fire TV Stick 4K Max 2nd Gen (2023)