Add EWoRA to PEFT

### Feature request

This is a second attempt (prev. issue #2970 was closed.)

Feature request
We propose to add EWoRA to the peft library -
https://aclanthology.org/2025.findings-ijcnlp.108/

This paper was accepted to the Findings of AACL-IJCNLP. It improves finetuning on a diverse downstream dataset through a mixture-of-experts approach.

Your contribution
I am able to create a PR for this.

### Your contribution

I am able to create a PR for this.

Read the cited EWoRA paper and compare its proposed mixture-of-experts approach with the existing PEFT library. Determine the integration scope and acceptance criteria before starting; done means EWoRA is supported as a PEFT feature with appropriate validation.

Written by the indexing model from the issue text.