Refactor and update types and handlers

- README changes: removed 'as const' annotation and note.
- Connector changes: dispatched event for commands in gateway.
- Updated processor type guard for command handlers.
- Removed readonly from CommandHandler types in handler definitions.
- Test adjustments: updated demo tests to reliable command registration.

README.md

@@ -70,7 +70,7 @@ const avatarCommand = createCommandHandler({
             description: 'The user to get the avatar for',
             required: true
         }
-    ] as const,
+    ],
     execute: async (context: Context, args) => {
         // Args will be typed here as { user: User }
         context.reply(args.user.avatarURL);
@@ -85,8 +85,6 @@ client.applicationCommands.register('avatar', ApplicationCommandType.Chat, avata
 // <...>
 ```
 
-> NOTE: The `as const` is required to ensure the types are resolved correctly. This is to work around some TypeScript weirdness.
-
 ## Hydration
 
 Hydration allows you to fetch and fill data on Discord objects. This is useful for when you need to fetch additional data about an object.