Feature request: Allow fetching blueprints from url with credentials.

[andreilupu]

I wonder if this line here is meant to be used for CORS handling only or is required for other purposes.
https://github.com/WordPress/wordpress-playground/blame/7b3b40253ea468ecf48ceaa7bba5d525f045dc89/packages/playground/website/src/lib/state/url/resolve-blueprint-from-url.ts#L16

I've made a private, self-hosted version of Playground, where I've protected the blueprint.json and the plugin zip files under an nginx OAuth2 proxy. Generally, this works well, except for the blueprint.json file, which is not loaded since the OAuth cookie won't be passed in that fetch.

Basically, I need an option to allow credentials: 'include' for private blueprints.

I was thinking of proposing a PR to make that a parameter, but I want to make sure this is in line with the project's principles.