Document node label sizing in draw function

[saikumarvasa100-hash]

Added documentation note clarifying that the draw() function does not currently support customizing node label sizes. Provided alternative approaches for users who need label customization.

Fixes #500

[maximelucas]

Thanks @saikumarvasa100-hash for this contribution!
Actually I've just realised: it is possible to control the label size from xgi.draw() through its kwargs:

H = xgi.Hypergraph([[1, 2, 3]])
xgi.draw(H, node_labels=True, font_size_nodes=20)
plt.show()

produces

font_size_nodes is not an explicit argument of draw() but it is passed down to draw_node_labels() of which it is an argument.

So the better alternative may be to write a note about these kwargs in general, not just the label font size?
And in any case I agree that it's still easier to use the dedicated draw_node_labels().