Add two pane view to calendar panel (#18286)

Co-authored-by: Paul Bottein <paul.bottein@gmail.com>

src/components/ha-button.ts

@@ -17,6 +17,9 @@ export class HaButton extends Button {
       .mdc-button {
         height: var(--button-height, 36px);
       }
+      .trailing-icon {
+        display: flex;
+      }
     `,
   ];
 }