Update README.md with extensive list of location rules and values

[EHLOVader]

This adds the possible values to the rule types that were previously listed.

I couldn't quite wrap my head around the formatting. Github flavored markdown doesn't support merged cells so a table didn't seem quite right.

I might be able to do HTML tables instead if this formatting isn't good.

I also wonder if the file formats for attachments is really necessary, it is what they include but I can't really figure out why they have ALL of those.

If accepted and merged can you label this PR with #hacktoberfest-accepted

Thank you.

EDIT: Realized this being Markdown might be tougher to review the changes. Here is the formatted view on my branch https://github.com/Log1x/acf-builder-cheatsheet/blob/37b3b32dabdfbbf434143dba33beeb1a1d3d8f8a/README.md#field-group-locations