fix(playground): fix the broken playground

[e111077]

update playground-elements to v0.20.0 which is more resilient to missing modules, and switch off of unpkg and onto jsdelivr for better stability

[Copilot]

Pull Request Overview

This PR fixes issues in the playground by upgrading the playground-elements dependency to v0.20.0 and shifting from unpkg to jsdelivr for improved module stability. Key changes include:

• Adding a cdnBaseUrl parameter to the playground plugin and associated environments.
• Modifying the content security policy in the server middleware to support jsdelivr.
• Updating components and site configuration to incorporate the new CDN base URL.

Reviewed Changes

Copilot reviewed 7 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/lit-dev-tools-cjs/src/playground-plugin/plugin.ts	Extended the plugin signature to include cdnBaseUrl and injected it into the litdev-example markup.
packages/lit-dev-tools-cjs/src/lit-dev-environments.ts	Added playgroundCdnBaseUrl to multiple environment configurations.
packages/lit-dev-server/src/middleware/content-security-policy-middleware.ts	Updated the connect-src directive to include jsdelivr.
packages/lit-dev-content/src/components/litdev-example.ts	Added a new property for cdnBaseUrl and updated the example template accordingly.
packages/lit-dev-content/site/_data/env.js	Included PLAYGROUND_CDN_BASE_URL for environment data.
packages/lit-dev-content/.eleventy.js	Passed the cdnBaseUrl to the playgroundPlugin in site configuration.

Files not reviewed (3)

• package.json: Language not supported
• packages/lit-dev-content/site/playground/index.html: Language not supported
• packages/lit-dev-content/site/tutorials/view.html: Language not supported

Comments suppressed due to low confidence (1)

packages/lit-dev-tools-cjs/src/playground-plugin/plugin.ts:231

• [nitpick] Consider using consistent quotation styles for HTML attribute values. For example, use double quotes for both sandbox-base-url and cdn-base-url to improve readability and maintain consistency.

        <litdev-example ${sandboxUrl ? `sandbox-base-url='${sandboxUrl}'` : ''}

[e111077]

https://pr1410-269b0f2---lit-dev-5ftespv5na-uc.a.run.app/playground/

[sorvell]

Thanks!