Some general updates, including initial 4.x updates

[deadbytefpv]

1. Notice about changing EdgeTX UI for colored-screen Radios.
2. Lua Script naming
3. Additional Baud Rate recommendations
4. New Lua Script options
5. Mentioning FlySky PA01
6. Linking Webflasher
7. ADC Filter setting for PWM receivers
8. Channel Mixing for PWM receivers
9. Moved BF Presets into Pre-First Flight page

I'll be making a separate PR for UI updates, unless someone has beat me to it.