[ENG-5373] site navigation (#1262)

* wip site navigation

* nav

* more nav stuff

* more navbar magic

* sidebar + navbar

* nav

* allow manual deploy-to-dev testing via dispatch

---------

Co-authored-by: pourhakimi <[email protected]>

Author: LineIndent

.github/workflows/deploy-dev.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+  workflow_dispatch:
 
 concurrency:
   group: deploy-dev

assets/bayesline_dark_landing.png

@@ -0,0 +1 @@
+## Some placeholder text ...