Using `oasdiff` for rich Git diffs of OpenAPI spec changes

I work with quite a few OpenAPI specs, and have found it useful to be able to keep an eye on what's changed over time. Although I'm familiar with the YAML (or JSON) representation of a given OpenAPI spec, it's nicer to have a summary that's human-readable. This especially is the case in my work maintaining rootly's Go SDK, where there's a lot of change! I've recently been using oasdiff a lot more, and have found that it'd be useful to have it as a diff driver for Git, so git diff output shows...