Define how DID Methods can specify paths and their dereferencing rules

[wip-abramson]

Created based on Discussion in https://www.w3.org/2025/05/29-did-minutes.html

We would need to point to the DID Extensions and state how different DID methods can define the path and processing rules they are using.

There is also an ongoing discussion in #150 around whether paths should be processed consistently across DID methods.