[Design] Deprecate wiki for contributing to the site

[danbrady]

Description

We have this wiki for contributing to the VADS. It has some good info in it but it is out-of-date and might be too high level for the type of contributions that we would like.

To do

Deprecate the wiki and add the helpful or useful content to the VADS directly.
@humancompanion-usds gets questions about which template to use for contributing. We have templates for different parts of the VADS that people can use. We need to make that more apparent.

Tasks

• Review the wiki and figure out what to bring over to the VADS
• Review the Updating this site page to make sure it is still helpful and relevant
• Add the content to the VADS either with a new page or a existing page
• Deprecate the wiki so it is no longer referenced on VADS

Acceptance Criteria

• Changes have been review with DST
• PR is approved with changes to the VADS