types(util): add case utility types (#683)

* types(util): add case utility types

* Rename *ID to *Id

src/handlers/commands/APPLICATION_COMMAND_CREATE.ts

@@ -5,14 +5,14 @@ export function handleApplicationCommandCreate(
   data: DiscordPayload,
 ) {
   const {
-    guild_id: guildID,
-    application_id: applicationID,
+    guild_id: guildId,
+    application_id: applicationId,
     ...rest
   } = data.d as ApplicationCommandEvent;
 
   eventHandlers.applicationCommandCreate?.({
     ...rest,
-    guildID,
-    applicationID,
+    guildId,
+    applicationId,
   });
 }