(buttons): Add Button<Context> interface.

src/types/button.d.ts

@@ -0,0 +1,6 @@
+import { ButtonInteraction } from "discord.js";
+
+export interface Button<Context> {
+  id: string;
+  execute(context: Context, interaction: ButtonInteraction, ...args: any[]): Promise<void>;
+}

src/types/index.d.ts

@@ -1,3 +1,4 @@
+export * from './button.d';
 export * from './command.d';
 export * from './database-types.d';
 export * from './event.d';