Document CSS bundles updates (#11526)
Document CSS bundles updates (#11526)

* updated docs to reflect new CSS bundles update

* PR fixes and fixed broken URL
flodolo/bedrock,pascalchevrel/bedrock,pascalchevrel/bedrock,alexgibson/bedrock,alexgibson/bedrock,craigcook/bedrock,pascalchevrel/bedrock,flodolo/bedrock,alexgibson/bedrock,craigcook/bedrock,mozilla/bedrock,flodolo/bedrock,mozilla/bedrock,pascalchevrel/bedrock,flodolo/bedrock,craigcook/bedrock,mozilla/bedrock,craigcook/bedrock,mozilla/bedrock,alexgibson/bedrock