Provide a link to gh-pages hosted docs

[natecook1000]

Swift Package Index is currently building docs in the 6.1 build, which doesn't work for this packge. We can self-host until that changes.

Checklist

• I've added at least one test that validates that my change is working, if appropriate
• I've followed the code style of the rest of the project
• I've read the Contribution Guidelines
• I've updated the documentation if necessary