Ask the user whether they want to register a TNUM

[markuspf]

Maybe this is an advanced feature.

[fingolfin]

That seems indeed rather advanced. It also only required editing the C file... So I am not convinced this is something that really needs to be added to PackageMaker...?

But if, then one can simply borrow parts of https://github.com/gap-packages/RegisterPackageTNUMDemo/blob/master/src/RegisterPackageTNUMDemo.c -- this, pluse perhaps an extra .tst file testing the relevant code, should be enough for that option. Of course instead of an option, one might also simply always generate the relevant code...