export wstest

Pipe function here: https://github.com/nhooyr/websocket/blob/master/internal/test/wstest/pipe.go#L17 is inside the internal package which means it can't be imported by other projects.
However it should be external so that it can be imported by other projects. This could help in unit testing of the projects

Start with internal/test/wstest/pipe.go at line 17 and inspect how the Pipe function is packaged and referenced. Make the utility importable by external Go projects while preserving its testing purpose, then verify that downstream projects can access it without relying on the internal package.

Written by the indexing model from the issue text.