Added SockJS definition

See https://github.com/sockjs/sockjs-client

Created manually by inspecting the various parameters
and return values.

There are seperate events, since, although SockJS
exposes a Websocket-like interface, it's not 100% same.

sockjs/sockjs.d.ts

@@ -0,0 +1,40 @@
+interface SockJSSimpleEvent {
+    type: string;
+    toString(): string;
+}
+
+interface SJSOpenEvent extends SockJSSimpleEvent {}
+
+interface SJSCloseEvent extends SockJSSimpleEvent {
+    code: number;
+    reason: string;
+    wasClean: bool;
+}
+
+interface SJSMessageEvent extends SockJSSimpleEvent {
+    data: string;
+}
+
+interface SockJS extends EventTarget {
+    protocol: string;
+    readyState: number;
+    onopen: (ev: SJSOpenEvent) => any;
+    onmessage: (ev: SJSMessageEvent) => any;
+    onclose: (ev: SJSCloseEvent) => any;
+    send(data: any): void;
+    close(code?: number, reason?: string): void;
+    OPEN: number;
+    CLOSING: number;
+    CONNECTING: number;
+    CLOSED: number;
+}
+
+declare var SockJS: {
+    prototype: SockJS;
+    new (url: string, options?: {
+         debug: bool;
+         devel: bool;
+         protocols_whitelist: string[];
+     }): SockJS;
+
+}