created a Micro:bit v2 test app, similar to the Hail test app

[qpalzmz112]

This app tests the supported libtock-c libraries on the Microbit. It has limited usefulness without using tockloader listen, but some tests use the LED matrix to display results.

[brghena]

We talked about this and qpalzmz112 knows the next steps to fix the format and build CI issues. Ping me when they're fixed and I'll do a full review of the code.

[qpalzmz112]

@brghena I made the changes we talked about!

[brghena]

@alexandruradovici Any opinions on what you want to see in a Microbit test app? This looks pretty great to me.

[brghena]

bors r+

[bors[bot]]

Build succeeded:

• ci-build (ubuntu-20.04)
• ci-format (ubuntu-20.04)