Customisations for Arduino UNO R4 WiFi board with 12x8 display

[kevinjwalters]

I plan to add some specific features for the relatively new Arduino UNO R4 WiFi board.

1. Use the 12x8 display as a bar chart similar to how the one works on BBC micro:bit in MakeCode.

Other changes not specific to UNO R4 WiFi

1. Improve mains interference rejections by tweaking buffer size. (Also covered by Change buffer size from 128 to 150 to further reduce effect of mains hum #41)

[kevinjwalters]

An R4 WiFi can be seen in action in Instructables: XX and https://www.youtube.com/watch?v=R6umD3_ovNo