New Audioscope effect

Addition of an oscilloscope for the audio signal with positive triggering and a frequency counter based on Tuner code.

• Gadgetoid#14

Tested in: https://www.youtube.com/watch?v=vYheu_LeiJY

A5 880Hz doesn't work due to upper 500Hz limit in the code at the moment.

Addition of Bluetooth logo

Adding a Bluetooth logo title screen for the Bluetooth uf2 while it waits for a device to connect.

First unicorn-audio-display release with Bluetooth bugfix

This is the first release of an enhanced version of Blunicorn with a waterfall spectrogram, an instrument tuner, and support for analogue input using DMA in a separate uf2.