Add PageNavigationHelper

  * Highlights sidebar link if currently visited
  * Adds deprecated label in sidebar for pages having deprecated: true
  in their YAML front matter.
Port example code blocks to Bootstrap
Style tables
Remove extra line from code blocks
Include Ubuntu Mono font
Fix path to favicon
Create /docs page
Reduce padding and change bottom of Back to Top button
Style Back to Top button for small screens
Change body background color
Minor color adjustment for example code blocks
Change TOC list item type
Style toggle button of example code blocks
Set Overview as index page for Authentication documentation
Style headings
Style sidebar
Re-order API versions
Rename Docs to Documentation
Rename flavor_data to settings
Featured Icons by @fotos