Add style guide to README #1180
Description
Related to a discussion on slack, it would be useful to have a style guide for new content as something to review against and also as a way to memorialize / close out issues like #1126 once a decision is made.
From @cmaimone (on slack):
I think adding a page of documentation about style would be the first step - linked prominently from the readme. There are some things we can add about how we handle the US-RSE name, RSE as an abbreviation, etc.