add URL parameter authentication support

[tantara]

Summary

Allow authentication via URL parameter as an alternative to HTTP Basic Auth header. This enables authentication in scenarios where headers cannot be easily set.

Background

I'm building a react library react-ttyd to integrate ttyd with react applications. Since browser doesn't allow to update header with WebSocket, I parse and verify credential from url parameters.

Example

ttyd --writable --credential testuser:testpw bash

socket = new WebSocket("http://localhost:7681/ws?authorization=${btoa('testuser:testpw')}", ["tty"]);

curl -X POST "http://localhost:7681/token?authorization=dGVzdHVzZXI6dGVzdHB3"
or 
curl -X POST  -H "Authorization: Basic dGVzdHVzZXI6dGVzdHB3" "http://localhost:7681/token"