Make some dependencies optional

[jtpio]

Thanks for putting this library together!

Currently there seems to be quite a few dependencies listed here:

py-maplibregl/pyproject.toml

Lines 13 to 20 in e0ae296

	python = ">=3.9,<4"
	shiny = ">=0.7.0"
	htmltools = ">=0.5.1"
	jinja2 = ">=3.1.3"
	pydantic = ">=2.5.3"
	anywidget = ">=0.9.0"
	pandas = {version = "^2.1.4", optional = true}
	geopandas = {version = "^0.14.2", optional = true}

But it looks like some of them may not be necessary in some situations. For example JupyterLab users may not need the dependency on shiny.

So maybe it would be possible to move some of these to an extras group?

[jtpio]

As a side-effect, this could help allow running maplibre in a WebAssembly environment like JupyterLite, which could then also enable some nice use cases such as hosting example notebooks on GitHub Pages, with everything running in the browser.

However it does not seem possible to install maplibre in JupyterLite at the moment when testing on https://jupyterlite.github.io/demo/lab/index.html, due to these extra dependencies:

import micropip
await micropip.install('maplibre', keep_going=True)