Some error messages (e.g. from Elm) are quite verbose, and are very hard to read properly without line breaks.

Therefore it would be nice if the vscode.Diagnostic message could contain line breaks (these could be stripped out in the Errors and warnings selector to keep the UI sensible). It would be even nicer still if error messages could contain colors and styles.

This is an example of the kind of thing it would be nice to have in a diagnostic popup: