Update Nextcloud theme

nextcloud/cwchristerw/custom.css

@@ -3,6 +3,10 @@ Christer Warén
 https://git.waren.io/cwchristerw/themes
 */
 
+img {
+  max-width: 100%;
+}
+
 header#header {
 background-color: #000000dd !important;
 }