[BUG] PERMAS .gz extension does not create zipped file

[martin-bernhard]

Describe the bug The export to the PERMAS file format supports the two extensions *.dato.gz and *.post.gz but does not create a zipped version of the ASCII file formats *.dato and *.post.
I was expecting the same behaviour like it is implemented for NETGEN.

To Reproduce Convert the test file box.med into PERMAS file box.post.gz.
meshio convert box.med box.post.gz

Diagnose The output is not a zipped mesh file, but a simple ASCII file only.