add protocols option to WebSocket constructor

This commit adds an option bag to the WebSocket constructor that allows
settings the protocols. This will bring interop between browsers and
server environments that already implement this (Bun and Node).

Closes: whatwg#42

index.bs

@@ -209,7 +209,7 @@ enum BinaryType { "blob", "arraybuffer" };
 
 [Exposed=(Window,Worker)]
 interface WebSocket : EventTarget {
-  constructor(USVString url, optional (DOMString or sequence<DOMString>) protocols = []);
+  constructor(USVString url, optional (DOMString or sequence<DOMString> or WebSocketInitDict) protocols = []);
   readonly attribute USVString url;
 
   // ready state
@@ -233,6 +233,10 @@ interface WebSocket : EventTarget {
   attribute BinaryType binaryType;
   undefined send((BufferSource or Blob or USVString) data);
 };
+
+dictionary WebSocketInitDict {
+  sequence<DOMString> protocols = [];
+};
 </xmp>
 
 Each {{WebSocket}} object has an associated <dfn for="WebSocket" lt="internal-url">url</dfn>, which
@@ -330,6 +334,8 @@ It can have the following values:
     "{{SyntaxError}}" {{DOMException}}.
  1. If |urlRecord|'s [=fragment=] is non-null, then throw a "{{SyntaxError}}" {{DOMException}}.
  1. If |protocols| is a string, set |protocols| to a sequence consisting of just that string.
+ 1. Otherwise, if |protocols| is a dictionary, set |protocols| to
+    |protocols|["{{WebSocketInitDict/protocols}}"]
  1. If any of the values in |protocols| occur more than once or otherwise fail to match the
     requirements for elements that comprise the value of
     \`<a http-header>`Sec-WebSocket-Protocol`</a>\` fields as defined by The WebSocket protocol,