Consider using the same node version in github actions workflows as in the app itself

[cullylarson]

We recently ran into an error caused by using node v16.5.0 (c.f. #274). It wasn't caught by the CI tests because they use node 16x, which just pulls the latest version of node. We should consider pinning the same version of node in CI as we define in the app, if that's possible. That way we'll catch issues like this in CI tests.