v0.4: Useful MIDI port names

New to CircuitPython 9.1 is the ability to set the USB MIDI port names.
This update includes the needed boot.py file to make that work.
Now picoslidertoy will show up as picoslidertoy in MIDI apps.

Note: OSes will often cache these names, so the old name will still show up for a while. On MacOS, you can run the "Audio Midi Setup" app and delete the "Pico" entry in the "MIDI Studio" / "Interfaces" section. (must have the picoslidertoy unplugged for this). Another option I think is to reboot your system.

To install this new UF2, put the board in UF2 mode and copy the "midi_sliders.uf2" file to the RPI-RP2 disk.
Instead of holding down the BOOTSEL button while powering on, you can also open the REPL and paste this one line in:

import microcontroller; microcontroller.on_next_reset(microcontroller.RunMode.BOOTLOADER); microcontroller.reset()

v0.3: display hole-less production boards to fab

New set of boards sent to fab, this time with no mounting holes for the I2C OLED display, as variations in those displays cause issues with hole alignment.

Apps:

• hwtest -- simple on/off test of the touch sensors, no display needed. Use serial REPL to see results
• hwtest_display -- like hwtest but also outputs simple feedback via the display
• midi_sliders -- MIDI controller where the sliders emit CCs and the buttons send NoteOn/NoteOffs

v0.2: black production boards to fab

added enclosure stl, small reorg

v0.1: Boards sent to fab

pcb proto submitted to fab