Add `deltalake` backend

Is your feature request related to a problem? Please describe.
I am considering using feast but the main back-end we use is not supported, which is deltalake. Deltalake is the only data lake implementation that has read and write support without a JVM. This makes it fairly easy to build large data lakes with only Python but there is no easy way with out a feature store wrapper to make features easily accessible..

Describe the solution you'd like
Add deltalake as an officially supported back-end.

Describe alternatives you've considered
There aren't really any.