Update menu-align-right script

The script now works with the latest classes, and the demo has been
updated to include a test case for the script.
Keep track of JS availability
Navbar sliding in from the side
Dark theme doesn't need to override text-align
Border on top/bottom by default

Move the left/right border to desktops for the dark theme.
Don't close navbar when it is clicked
Use matchMedia to limit JS functionality
Add icon fonts