Add Equatable conformances to new types

Author: kateinoigakukun

Diff for: Sources/JavaScriptKit/BasicObjects/JSPromise.swift

@@ -32,7 +32,7 @@ public final class JSPromise: JSBridgedClass {
     }
 
     /// The result of a promise.
-    public enum Result {
+    public enum Result: Equatable {
         /// The promise resolved with a value.
         case success(JSValue)
         /// The promise rejected with a value.

Diff for: Sources/JavaScriptKit/JSException.swift

@@ -12,7 +12,7 @@
 ///     let jsErrorValue = error.thrownValue
 /// }
 /// ```
-public struct JSException: Error {
+public struct JSException: Error, Equatable {
     /// The value thrown from JavaScript.
     /// This can be any JavaScript value (error object, string, number, etc.).
     public var thrownValue: JSValue {