Content Versioning, Slack Link

Tickets

Add version flag to content front matter and environments #697
Update "Join HCA slack" link #700
Fix button text positioning of "Show Required Fields Only" button #703
Update external links #709

Commits

be8ca14 Gatsby node refactor. Ordering metadata navigation by lowercase. #697.
8fbc028 Update external links. Resolves #709.
5787d82 Add version flag to content front matter and environments. Linting. Resolves #697.
ee5400e Match staging.
4b5934e Add version flag to content front matter and environments. Review of internal links. Resolves #697.
dd1ef5d Add version flag to content front matter and environments. Resolves #697.
713898a Update 'Join HCA slack' link. Resolves #700.
619e370 Fix button text positioning of 'Show Required Fields Only' button. Resolves #703.