Update index.html.md - noted that geo spreadsheet can be only accessed by...

Why is this change being made?

Clarified who can access the geo spreadsheet. This will help to clarify who the spreadsheet can be accessed by (as I have gotten some requests from non-employees).

Update index.html.md - noted that geo spreadsheet can be only accessed by employees (per discussion with our rep at LinkedIn) and also added some additional sites to list roles.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for the proposed change, per say-why-not-just-what