Update pkgdown website home page

[Bai-Li-NOAA]

The pkgdown site is live now. The dictionary terms and R functions documentation can be found under the reference page.

To update the home page, we still need to

• [ ] Update DESCRIPTION (e.g., title, license, and authors)
• [ ] Update README.md
• [ ] Update citation
• [ ] Change package name following the tips here