Refactor + add message box.

src/components/common/user/UserCheckbox.tsx

@@ -0,0 +1,14 @@
+import { User } from "revolt.js";
+import UserIcon from "./UserIcon";
+import Checkbox, { CheckboxProps } from "../../ui/Checkbox";
+
+type UserProps = Omit<CheckboxProps, "children"> & { user: User };
+
+export default function UserCheckbox({ user, ...props }: UserProps) {
+    return (
+        <Checkbox {...props}>
+            <UserIcon target={user} size={32} />
+            {user.username}
+        </Checkbox>
+    );
+}