This PR implements `Transport` for WebTransport for browsers by using web-sys.
Related: #3846.
Resolves: #3825.
Pull-Request: #4015.
Co-Authored-By: Yiannis Marangos <yiannis@eiger.co>
Co-Authored-By: Maciej Zwoliński <mac.zwolinski@gmail.com>
Co-Authored-By: Yiannis Marangos <psyberbits@gmail.com>
