Create a website using pkgdown

[Bai-Li-NOAA]

We talked about creating a pkgdown website as a backup website of the Rstudio connect website. However, the pkgdown website cannot be built because the materials inside of the docs/ folder are not built by pkgdown. @ChristineStawitz-NOAA, how about we create a presentations/ folder for hosting slides? Then we can use pkgdown to create a docs/ folder and a website to show the 20 terms?

[Bai-Li-NOAA]

Get error message when building the website:

1: In '_pkgdown.yml', topic must be a known topic name or alias
x Not 'Projection' 
2: In '_pkgdown.yml', topic must be a known topic name or alias
x Not 'make_full_web' 
3: In '_pkgdown.yml', topic must be a known topic name or alias
x Not 'make_hex' 

Remove them from the _pkgdown.yml, but still need to work on Projection.R, make_full_web.R, and make_hex.R to fix the error.