fix calendar event modal background overflow

Fixes missing background while scrolling long
calendar event descriptions.

Signed-off-by: Marvin Frommhold <depressiveRobot@users.noreply.github.com>

Author: depressiveRobot

src/components/calendarModal.module.css

@@ -24,6 +24,7 @@
     max-width: 100%;
     width: 500px;
     background-color: #fff;
+    overflow-y: scroll;
 }
 
 .modalTitle {