feat(cdn): allows customization of the CDN base url

[e111077]

Allows for setting the CDN base url. Currently only tested is unpkg and https://cdn.jsdelivr.net/npm via the cdnBaseUrl property and config entry

[e111077]

Had to change the package.json because unpkg can't serve 2.8.0 for some reason but it can 3.0.0 so this unbreaks the default case in the configurator

[sorvell]

Thanks so much! optional nits.

[e111077]

Test failure seems like a flake

[augustjk]

do we need this as a separate property on <playground-project> if it's already part of the config property, or the JSON in projectSrc?

[e111077]

The idea was that the property takes precedence over the config and if neither are defined then it defaults to unpkg.com. But actually what you're pointing out right now as well is that by setting this default on the property, it will by default not read from the config unless you explicitly set ''

I'll work on a lower priority followup to this

[e111077]

#423 but I think your original question is still valid. It's a decision I made to support both. My reasoning was that if we wanted to set this across lit.dev, we'd only have to change the base config that is shared across basically all the projects

[augustjk]

yeah keeping it in the JSON manifest for the project-src or config property which share the same interface makes sense, and that'll allow us to update that for the whole of lit.dev playground in relatively few places since we extend from just a few base project jsons.

adding the extra cdnBaseUrl property on top of that to <playground-project> that overrides the project manifest doesn't seem as necessary to me and we'd have to clearly document which value takes precedence if we do keep it.