Consider supporting HTTP and non-privileged ports for "localhost" DIDs

[vdods]

In order to ease testing of VDRs, it would be useful to allow unencrypted HTTP and use of an arbitrary port for "localhost" DIDs. Just as in https://w3c-ccg.github.io/did-method-web/#method-specific-identifier the colon should be percent-encoded in order to distinguish it from the path components of the DID. When the domain of the DID is "localhost", then http:// should be used in the DID resolution process instead of https://, because typically the service being tested will not have TLS enabled.

[vdods]

Support for non-standard ports has been added in main branch in commit c8ee9f4 though support for use of plaintext HTTP requests is limited to use of DID_WEBPLUS_HTTP_SCHEME_OVERRIDE env var for now.