flesh out sidenav drawer

[jamisonvalentine]

• [x] make collapsible
• [x] hightlight link on hover
• [x] change menu items font
• [x] add icons
• [x] animated menu button: https://www.w3schools.com/howto/howto_css_menu_icon.asp

[ebgoldstein]

I'm folding the stray tasks from https://github.com/UNCG-DAISY/StormImpactMap/issues/16 into this issue:

• [x] liability statement (i can write this)
• [x] a link back to the github repo
• [x] acknowledgement where NOAA +USGS + ML data comes from (i can write this)

[jamisonvalentine]

will open separate issue to improve appearance of modal content