[Feat] [pydeck] Allow overriding CDN URLs

[bijanvakili]

Target Use Case

By default, pydeck references the JSDelivr Content Delivery Network in its URL to download embed the @deck.gl/jupyter-widget Javascript package which includes all required deck.gl packages.

• Default URLs are specified here.
• Uses semantic version specification here

There may be cases where clients may not wish to use a different CDN with pydeck (e.g. need different terms of use, service level agreements, etc.).

Proposal

pydeck.Deck itself need to be built to allow overriding the URLs by including a cdn_urls dictionary with the JS package names (@deck.gl/jupyter-widget) and (@deck.gl/jwidget) as keys. This would easily allow for more URLs in the future. This dictionary could then be propagated to the logic in cdn_picker here to
override both bundle URLs if required.

If the cdn_urls kwarg is not provided or any of its keys are missing, it can default to the current behavior.