Create .config folder if it doesnt exist

[logsol]

On a freshly installed Raspbian 64bit OS (lite) the ~/.config folder is not created yet and the script fails with this error:

System version:

Raspberry Pi OS arm-64bit (2022-01-28)

Specify install location for Pianoteq

Traceback (most recent call last):
  File "/home/pi/pianoteq/setup.py", line 320, in <module>
    with dbm.open(CONFIG_PATH, 'c') as db:
  File "/usr/lib/python3.9/dbm/__init__.py", line 95, in open
    return mod.open(file, flag, mode)
_dbm.error: [Errno 2] No such file or directory: '/home/pi/.config/pianoteq-pi.dbm'

This should be checked and created.