Run the e2e tests selectively on relevant changes.

[beeman]

We should update the e2e-test workflow to only run the tests when relevant files change.

For example, if we change the README like here #153 it should not run.

---

also worth considering: only running the test templates action when the the src dir or specific config files changes (like package json). This should prevent the excess runners when they are not needed

Originally posted by @nickfrosty in #150 (comment)