Should the source view suggest enabling the "JS Sources" feature?

Now that JS source support has landed in Nightly, I tried it a few times but it wasn't working. On the third try I finally remembered that I need to enable a feature on about:profiling. I would have realized earlier if the error message in the source view had given me a hint.

Should we add such a hint? Or are we planning to have it work by default soon?

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-936)