Collapse message bubbles when applicable

ts/components/AvatarSpacer.tsx

@@ -0,0 +1,12 @@
+// Copyright 2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { ReactElement } from 'react';
+import React from 'react';
+import type { AvatarSize } from './Avatar';
+
+export const AvatarSpacer = ({
+  size,
+}: Readonly<{ size: AvatarSize }>): ReactElement => (
+  <div style={{ minWidth: size, height: size, width: size }} />
+);