Changes to documentation section with new server card.

[zorkow]

Changes as discussed in our f2f:

• Getting started button in the header.
• Documentation button now points to docs pages.
• Documentation section is now getting started section.
• Added a card for server integration.
• Improved the back-linking from the close buttons to the cards.

[zorkow]

Included all suggestions. PTAL. I will do security updates in a separate PR.