Mighty 20BT support

[mjteebone]

First of all - many thanks for starting this project to make BT footswitch for Mighty's. This really opens up totally new 'usability' of these amps.
I wanted to propose to also include the Mighty 20BT amp (I use the 1st Gen). It is managed by the same android app on the phone, however the logic is slightly different - there are four double banks = 8 presets in total but the configuration between banks is limited comparing to Mighty plug where you can use whatever preset in in whichever memory bank. In Mighty 20BT you have hardcoded channels per bank: CLN, OD, METL, LEAD and in each bank you can configure two presets. A dedicated footswitch would have to work somehow different, instead of cycling through the presets, you would need to set more buttons and be able to select bank/preset directly. Just an idea to pick up if possible. I will also try to dig the code myself to see how this can be achieved.