Create shared website theme styles

[WillBAnders]

Create styles for a shared website theme (primarily in the context of the landing page). These should be reusable between pages/components.

Requirements

• Colors: Mix of blues; see Slide theme for examples.
  • Check contrast for accessibility.
• Font: Poppins (Next seems to have access to Google fonts already; should be able to leverage that)
• If time/interest allows:
  • See if you can utilize the existing code for light/dark modes to support both. Not sure if we'll really use this, but could be something to look at.