[Task] Add support for DLT-less methods

[eike-hass]

Description

Add support for additional DID methods that follow other CRUD implementations then did:iota. Off-chain methods like did:key or did:jwk can be a good proof of concept and are useful by themselfes.

Motivation

Describe the motivation for the feature to be developed.

Resources

Link to any resources relevant for the task such as issues, PRs, reference implementations, or specifications.

To-do list

• refactor did:key
• add did:jwk
• add 'did:web'

Change checklist

Add an x to the boxes that are relevant to your changes, and delete any items that are not.

• The feature or fix is implemented in Rust and across all bindings whereas possible.
• The feature or fix has sufficient testing coverage
• All tests and examples build and run locally as expected
• Every piece of code has been document according to the documentation guidelines.
• If conceptual documentation (mdbook) and examples highlighting the feature exist, they are properly updated.
• If the feature is not currently documented, a documentation task Issue has been opened to address this.