Add rate of change filter (or sensor)

**Describe the problem you have/What new integration you would like**

Ability to convert raw values to the rate of change over some window size. I.e. current value minus last value or an average of previous x values.

**Please describe your use case for this integration and alternatives you've tried:**

I've made a bed occupancy sensor using a load cell but there is a lot of drift even after calibration. Since I don't really need the exact weight I want to count the bed as occupied if either of these conditions have been met in the last 5 minutes: 1) Current weight is above the average weight in the last 24 hours or 2) the absolute value of the current value minus the last value is above 1kg.

The automation rules can be handled in home assist but I need to be able to create a rate of change filter (or sensor? i.e. it could be a copy of an existing sensor with filters to facilitate multiple values) in esphome.

**Additional context**

Thanks again for creating esphome, its been an awesome piece of software to improve my home automation and tinker with electronics and components I'd never have otherwise played with.