Added details in Known Issues for skipped evaluations for managed RGs (Microsoft.Databricks/workspaces & Microsoft.Solutions/applications), updated some formatting in README

[shanhix1]

Summary of changes in this PR:

• Moved description from header Optional or auto-generated resource property that bypasses policy evaluation to header Resources that are exempt from policy evaluation.
• Added additional details around behavior of databricks managed RG resources skipping evaluation on cross tenant calls (creation time only, when the RP deploys the resources)
• Added callout for skipped evaluation in RGs managed by Microsoft.Solutions/applications too
• Added tik marks for the resource types in the new section I added. Then added tik marks for aliases & resource types throughout the README for consistency.

Main change: