did-example Rust implementation

An easy way to create and read example DID's that do not need to be deterministic.

Example DID Documents need to be manually added to the resolver to work as the Document cannot be automaticallyr esolved.

lib.rs:

• This module is a simple example of a DID resolver that uses a cache to store DID documents.
• Should only be used for local testing and development
• Enable using the did_example feature flag