[Feature Request] Provide Cursor Implementation in embedded-io

[overcat]

Description

I've encountered a need for Cursor while using embedded-io. The current codebase doesn't seem to provide this feature, so I implemented it myself. However, I'm unsure if adding a Cursor to this repository aligns with the project's goals.

Motivation

A Cursor can be useful for navigating through data streams or buffers, and it might benefit other users. I wanted to check if this feature would be a good fit for embedded-io.

Proposal

If this is something you'd consider adding, I can submit a pull request with the implementation. Looking forward to your thoughts!