[Community] Hypernetworks

**Is your feature request related to a problem? Please describe.**
Support for hypernetworks since they seem to yield great results. An example can be seen here:
https://github.com/AUTOMATIC1111/stable-diffusion-webui/blob/master/modules/hypernetworks/hypernetwork.py

info: https://github.com/AUTOMATIC1111/stable-diffusion-webui/discussions/2670

**Describe the solution you'd like**
A diffusers hypernetwork implementation that is compatible with Automatic's implementation

**Describe alternatives you've considered**
Switching back and forth between different repos, but a one-stop shop is preferred.

Review the referenced Automatic1111 implementation in modules/hypernetworks/hypernetwork.py and the linked discussion for the expected behavior and compatibility requirements. Compare those requirements with the current diffusers project before defining the integration scope; done means a diffusers hypernetwork implementation compatible with Automatic's implementation.

Scritto dal modello di indicizzazione a partire dal testo della issue.