Tracking costs

[fcastilloec]

Checklist

• I have filled out the template to the best of my ability.
• This only contains 1 feature request (if you have multiple feature requests, open one feature request for each feature request).
• This issue is not a duplicate feature request of previous feature requests.

Is your feature request related to a problem? Please describe.

I would like to track cost. I'm not sure if National Grid provides this information with their new API, but if possible. This would be great.

Describe the solution you'd like

Have an entity that tracks the total costs or that tracks the current price. For both gas and electricity.

Describe alternatives you've considered

Home Assistant offers the option to set a static price, but as soon as an entity is added, the option is grayed out (as well as the option to track with a current-price entity). This happens to both electricity and gas tracking.
The problem might not be trivial, specially when National Grid offer pricing for delivery and supply, and people might use a different supplier. The information might not be available through the API, but a rough estimation can be done based on last bill cost and usage.

Additional context

I don't think the opower based integration had this information, but given that there was a change in API, perhaps this is now possible