Should we add a pkgdown web site?

Should we add a pkgdown web site? It might be a better linkable resource for describing the project. I think the effort required is low. The basic procedure is at https://pkgdown.r-lib.org/

We would need to do these things:

Add .github/workflows/pkgdown.yaml by stealing pkgdown.yaml
Add _pkgdown.yml
Make a NEWS.md formatted like NEWS.md, while stealing and summarizing CHANGELOG content from psofa and nSOFA_calculation
Maybe add this to .RBuildignore
```
^_pkgdown\.yml$
^docs$
^pkgdown$
```
Maybe add this to .gitignore
```
docs
```

ctsit / sofa

Should we add a pkgdown web site? #3