Fix Typos and Improve Documentation Clarity in CHANGES.md and echo/README.md

[sky-coderay]

Pull Request Description

Changes Introduced:

1. CHANGES.md:

   • Fixed the term "multiadress" to "multiaddress" for accuracy and consistency in the WebTransport metrics description.
   • Clarified the WebTransport update explanation for certificate hash usage when listening on WebTransport.

2. examples/echo/README.md:

   • Fixed repeated typo "with send" to "will send".
   • Fixed repeated typo "be used preferentially" to "be used preferred".

This PR focuses on documentation improvements, aligning the project with high standards for clarity and professionalism.

[sukunrt]

I'm gonna close this, it isn't meaningful enough, or correct for that matter(used preferentially is better compared to used preferred).

You can check the https://github.com/libp2p/go-libp2p/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22 (good-first-issues) label for more substantial contribution opportunities.