Highlighting of multi-line `if` fields

Is your feature request related to a problem? Please describe. I often use a complex if field to enable smart skipping of the push event trigger. (note that without the ${{ }} the editor yields a syntax error saying Unexpected symbol: '=='. Adding a space after the initial ! seems to eliminate the error, but I'm not sure if that works (#290).)

Writing it like that looks horrible so I format it as a multi-line string, but then the syntax highlighting is broken.

Describe the solution you'd like It would be really nice to have syntax highlighting for multi-line expressions. It would look something like this: