Universal functions

[dbuezas]

Work in progress. Implementation of #130

• Functions are allowed everywhere with this format:

type: custom:plotly-graph-dev
entities:
  - entity: sensor.garden_temperature
    offset: $fn () => "0d"
    name: |
      $fn({ys, vars}) => {
        vars.title = ys[0];
        return ys[ys.length-1]
      }
  - entity: sensor.keller_humidity
title: $fn({ vars }) => vars.title
hours_to_show: 2