[MNT] Add missing distr:paramtype tag to Skellam, GumbelL, GumbelR, FDist, Rayleigh

[ANANYA542]

Describe the maintenance issue

Several distributions are missing the "distr:paramtype": "parametric" tag in their _tags dictionary. Methods like get_params_df() and to_df() rely on get_class_tag("distr:paramtype") == "parametric" to handle distributions correctly. Without this tag, these distributions are silently incompatible with parts of the framework API.
The following files are affected:

skpro/distributions/skellam.py
skpro/distributions/gumbel_l.py
skpro/distributions/gumbel_r.py
skpro/distributions/f_dist.py
skpro/distributions/rayleigh.py

All five are parametric distributions and should declare this tag, consistent with Normal, Cauchy, Exponential, and others that already do.

To Reproduce
pythonfrom skpro.distributions import Skellam, Normal
print(Normal.get_class_tag("distr:paramtype"))
(Returns: 'parametric')
print(Skellam.get_class_tag("distr:paramtype"))
(Raises ValueError: Tag with name distr:paramtype could not be found)

A screenshot of the reproduction output is attached below.

[ANANYA542]

hi @fkiraly — while investigating the Levy tag issue I raised earlier, I noticed the same "distr:paramtype": "parametric" tag is missing across a few other distributions as well. Went through the files and found five more affected — Skellam, GumbelL, GumbelR, FDist, and Rayleigh. If this is worth fixing I have bundled all five into a single PR please look into it