Update banner of rendered site

[somros]

• add GitHub icon
• add "Known limitations" tab
• Update link to wiki

[jacobkasper]

This all looks good but I am wondering about the link "Confluence Wiki." Is that misleading because it is no longer on the confluence site?

[andybeet]

agreed. should we keep the link in the appendix but just rename it? or add a link in resources? or add a link on the landing page? or maybe all of the below:

• add link on landing page
• add link in resources tab
• remove appendix link to confluence