What: Update Sandbox readme to explain process and community questions/comment expectations

[TheFoxAtWork]

Why:

• Current README does not provide sufficient information on expectations (projects or community members)

This change address the need by:

• adding more info about what occurs between application and review meeting
• provide information to projects on TAG, TOC, and community comments/questions
• advise community members on appropriate comments.

[dims]

LGTM