Inject custom variables

Ability to inject custom variables to helpers to use in helper names and other fields.

Create something like this on the page:

boei_vars {
name: "Dan",
company: "My Corp",
plan: "Pro",
}

Feedback helper: 👋 Got any feedback Dan?
Intercom helper: 🤔 Any questions about your Pro plan?
Email helper: Subject - "Question from Dan at My Corp (Pro plan)"