Add background info to meta refresh rules (bc659a, bisz58)

[carlosapaduarte]

Adds background info describing what a meta refresh is, to the meta refresh rules

Closes issue(s):

• closes #2151

Need for Call for Review:

• This will not require a Call for Review

How to Review And Approve

• Go to the “Files changed” tab
• Here you will have the option to leave comments on different lines.
• Once the review is completed, find the “Review changes” button in the top right, select “Approve” (if you are really confident in the rule) or "Request changes" and click “Submit review”.
• Make sure to also review the proposed Call for Review period. In case of disagreement, the longer period wins.