fix: replace Window type with reduced WindowLike type

If comlink is used with typescript, where only compilerOptions.lib "webworker" without "dom"
is configured, the error "Cannot find name 'Window'" is thrown. This PR replaces the Window
type with a custom type WindowLike that declares the minimal required functionality to work.

src/comlink.ts

@@ -16,7 +16,8 @@ import {
   Message,
   MessageType,
   WireValue,
-  WireValueType
+  WireValueType,
+  WindowLike
 } from "./protocol.js";
 export { Endpoint };
 
@@ -245,7 +246,10 @@ export function proxy<T>(obj: T): T & { [proxyMarker]: true } {
   return Object.assign(obj, { [proxyMarker]: true }) as any;
 }
 
-export function windowEndpoint(w: Window, context = self): Endpoint {
+export function windowEndpoint(
+  w: WindowLike,
+  context: WindowLike = self
+): Endpoint {
   return {
     postMessage: (msg: any, transferables: Transferable[]) =>
       w.postMessage(msg, "*", transferables),

src/protocol.ts

@@ -11,8 +11,7 @@
  * limitations under the License.
  */
 
-export interface Endpoint {
-  postMessage(message: any, transfer?: Transferable[]): void;
+export interface EventSource {
   addEventListener(
     type: string,
     listener: EventListenerOrEventListenerObject,
@@ -23,6 +22,18 @@ export interface Endpoint {
     listener: EventListenerOrEventListenerObject,
     options?: {}
   ): void;
+}
+
+export interface WindowLike extends EventSource {
+  postMessage(
+    message: any,
+    targetOrigin: string,
+    transfer?: Transferable[]
+  ): void;
+}
+
+export interface Endpoint extends EventSource {
+  postMessage(message: any, transfer?: Transferable[]): void;
   start?: () => void;
 }