create some functional tests in CI #43
Description
I don't know what parts of the js dependencies might end up in the compiled js for the prod site - would be good to have some automated browser testing for things like accordion in order to be confident merging dependabot PRs. I don't think they're hugely important - as we're not running npm live, we're compiling static assets - but even so, we could probably avoid a big overhaul job further down the line by keeping things up to date now.