Support for `data-test-*` properties on the JS class

[Turbo87]

If those properties are computed properties there isn't much we can do except skip the file, but we should be able to move literals into the template directly.

Example: https://github.com/rust-lang/crates.io/blob/ecba6b298fbbbb284f919354bfc02aaa2f5d3449/app/components/crate-row.js#L10