Update TMAP8 website

[simopier]

• Update config.yml to add links to important pages to header menu
• Update installation instructions for clarity
• Have users update on devel rather than main
• Update instructions to use TMAP8 to add link to examples

(Close. #95)

[moosebuild]

Job Documentation on f3663ec wanted to post the following:

View the site here

This comment will be updated on new commits.

[simopier]

@cticenhour I think that's good to go.