Document the specific of using the Flatpak version of PyCharm

[BrunoVernay]

Out of the box, there is not even a Python interpreter configured.
The user will generally search for their system interpreter. In my case was Python 3.8, yet PyCharm showed 3.7 since it is the one embedded in Flatpak. I don't know how I could install Python 3.8 or Conda in Flatpak environment. I see in the issues that the debugger might not be working either ...
At least, start a Wiki or something and people will (might) contribute.

[Tasm-Devil]

Have the same problem. Pycharm is finding /usr/bin/python3.7 but there is no such file on my system.
The flatpack is only usable with venv