Missing dependency for Ubuntu 20.04 package

[andrewfu77]

At least one dependency seems to be missing from ngsolve_6.2.2102-0~ubuntu20.04.1_amd64.deb from ppa:ngsolve/ngsolve: some (all?) of the ngsolve and netgen-related shared libraries have a dependency on libpython3.8.so.1.0, but although python3 is listed as a dependency, libpython3.8 is not. (Actually it should probably be libpython3.8-dev)