Add Documentation For Contributors

[rebeccaskinner]

The README.md document contains sufficient information for an interested contributor on the technical side of things, but we lack a clear process for how an interested contributor can get involved in the website. We should create documentation outlining the process for contributing to the website.

In addition to documenting the process, this issue should stand in as an opportunity for the community to comment on that process. If you are interested in contributing to the website and have input into what the contribution process should look like, please add comments to this issue.