[Docs] Improve Documentation Navigation

Reading Excalibur documentation can be difficult as you have to constantly go back to previous page to the parent document and then select the next section.

It would be good to have 'Next' , 'Previous' links to take you to next page in the current table of contents or to next section.

Start by locating the Excalibur documentation table of contents and the navigation setup that controls section order. Trace how readers move between documentation pages, then add Previous and Next links for adjacent sections. Done means readers can move through the current table of contents without returning to the parent page.

Written by the indexing model from the issue text.