feat: implement encodePointerUriFragment and consume it in pathToPointer

[P0lip]

Needed by https://github.com/stoplightio/platform-internal/pull/16345

Reference: https://datatracker.ietf.org/doc/html/rfc6901#section-6

Been a bug for a few years.

[stoplight-bot]

:tada: This PR is included in version 3.21.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: