Add support for the DIY Keyboard to mega65r[3456]

[tdeval]

Tested on my new R6.

When flashed to slot #0, the R6 works independently with the factory keyboard or the DIY.

Unfortunately, with the factory core 0.96 in slot #0 and the DIY keyboard hooked, the core selection menu flashes continuously. But as soon as this core is loaded, the DIY keyboard can be swapped and works immediately.

Links to Paul's blog articles:

• https://c65gs.blogspot.com/2022/10/mega65-mk-ii-keyboard-pcb-design.html
• https://c65gs.blogspot.com/2022/11/progress-on-diy-keyboard.html

[lydon42]

We (Paul and I) combined 804 and 808 (Wukong, which also changes keyboard stuff), into https://builder.mega65.org/job/mega65-core/job/804-808-mkii-kbd-wukong-newcore/

[lydon42]

Merged into 804-808-mkii-kbd-wukong-newcore.