feat: Add preview for attachment messages (#1562)

Add preview for pending messages and attachments

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

app/javascript/dashboard/helper/specs/files.spec.js

@@ -0,0 +1,18 @@
+import { formatBytes } from '../files';
+
+describe('#File Helpers', () => {
+  describe('formatBytes', () => {
+    it('should return zero bytes if 0 is passed', () => {
+      expect(formatBytes(0)).toBe('0 Bytes');
+    });
+    it('should return in bytes if 1000 is passed', () => {
+      expect(formatBytes(1000)).toBe('1000 Bytes');
+    });
+    it('should return in KB if 100000 is passed', () => {
+      expect(formatBytes(10000)).toBe('9.77 KB');
+    });
+    it('should return in MB if 10000000 is passed', () => {
+      expect(formatBytes(10000000)).toBe('9.54 MB');
+    });
+  });
+});