Make MarkdownRenderer async.

[ditman]

Description

Makes MarkdownRenderer return a Promise<string> to allow for async markdown rendering.

Also updates the Angular and Lit renderers to support the new async rendering.

Pre-launch Checklist

• I signed the CLA.
• I read the Contributors Guide.
• I read the Style Guide.
• I have added updates to the CHANGELOG.
• I updated/added relevant documentation.
• My code changes (if any) have tests.

If you need help, consider asking for advice on the discussion board.

[gemini-code-assist]

Code Review

This pull request successfully refactors the MarkdownRenderer to be asynchronous, returning a Promise<string>. The changes are correctly propagated throughout the Angular and Lit renderers, using appropriate mechanisms like Angular's AsyncPipe and Lit's until directive to handle the promises. The type definitions and tests have also been updated to reflect this change. My review includes a couple of minor suggestions to simplify the implementation of some of the new async functions for better code clarity and adherence to best practices.

[ditman]

I had to uncommit the changes to package-lock.json coming from my dev box so CI could continue. Also addressed PR feedback and applied formatting to the markdown-it package. I'm landing this!

[wwwshadyalfars1981992-hash]

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