Add ibus receiver support from upstream NFE Silverware

[jumper047]

Duplicate of my original PR (#16), but made from standalone branch

[jumper047]

I added new rx_switch value to this PR, and also opened new one to LiteOSD - BETAFPV/LiteOSD#5

[johnkerman]

@jumper047 hello!
Due to betafpv developers get stuck somewhere, can you please tell how to build this firmware with your changes?
Or its better to use already built assets from your fork release page?
My target is to use ibus receiver with beta65s lite whoop.

Thanks a lot!

[jumper047]

Hi @johnkerman !
If you want to install prebuilt binaries check this instruction - README.md INSTALL.md You'll need to flash OSD firmware too. If you need an ibus support only, just compile firmware from rx_ibus branch as regular silverware (see INSTALL.md, it contains link to rcgroups post with instructions).