Feature request: method to display all available versions of a graph

[justaddcoffee]

It would be handy to know what versions of a graph are available, especially for KG-Hub projects.

For example, it'd be nice to be able to do this:

from grape.datasets.kghub import KGCOVID19
KGCOVID19.versions()

and then choose a KG build to load

[justaddcoffee]

Adding - this functionality is kinda already implemented:

from grape import datasets
df = datasets.get_all_available_graphs_dataframe()
df[df['name']=='KGCOVID19']