Update home page to be more memorable and Pangeo 'branded'

[maxrjones]

This website was built off a clone of https://github.com/xarray-contrib/xarray.dev and retains much of that style. We may want to redesign the home page to better define a memorable Pangeo 'brand'. @andersy005 suggested that there may have been some branding materials (e.g., color scheme, style guide, assets) created early in the project which could guide this process. He also recommended https://penpot.app/ for design planning. We could also see if NumFOCUS could provide support with this task.