Autocreate files that prevent MacOS indexing of the CIRCUITPYTHON dive
Autocreate files that prevent MacOS indexing of the CIRCUITPYTHON dive

.. the price of this appears to be about 112 bytes of flash and 12
bytes of RAM, according to the stats printed during the build.

It also uses up 4 directory entries (out of 128), but does not reduce
the number of blocks usable for storing file contents.

These are the same items noted in the Adafruit README for Trinket M0
as preventing MacOS indexing.

Closes: #689

adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/micropython,adafruit/micropython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython