[Task] Trim Readme in `identity_iota` to reduce duplication

[wulfraem]

Description

Currently, the root level README file and the README in idenity_iota are duplicated. This is required to have a proper crate documentation in idenity_iota AND have a good entry point on GitHub.

We could add an automatic step during crate publishing, that just the root level README into the identity_iota folder.

Motivation

This way we could reduce the identity_iota README to a much shorter version and avoid having the README in two places, possibly diverging over time.