Feature Request: Use entity_id instead of variable

[Ex0danify]

I don't know if this extension is still actively maintained, but I'll write my proposal anyways.

With the current situation the service call to "set_variable" MUST contain the variables entity_id as key 'variable'.

Current Situation:
When calling the service with an entity_id supplied, Home Assistant will throw an error: "extra keys not allowed @ data['entity_id']"

Request:
Remove the required 'variable' from the service data and use entity_id instead.

I looked through the code, but I can't quite seem to understand where to change it to allow the passed entity_id to be used as variable (I have an understanding of coding in general, but sadly I haven't looked into development for Home Assistant yet.)

[skynet01]

+1 for this as I also have the same issue :)