Don't let images go over the available width

css/converse.css

@@ -1571,7 +1571,8 @@
         margin-top: 1em; }
     #converse-embedded-chat .chatbox .chat-body .chat-image,
     #conversejs .chatbox .chat-body .chat-image {
-      max-height: 24em; }
+      max-height: 24em;
+      max-width: 100%; }
     #converse-embedded-chat .chatbox .chat-body .chat-action,
     #conversejs .chatbox .chat-body .chat-action {
       font-style: italic; }

css/inverse.css

@@ -1617,7 +1617,8 @@ body {
         margin-top: 1em; }
     #converse-embedded-chat .chatbox .chat-body .chat-image,
     #conversejs .chatbox .chat-body .chat-image {
-      max-height: 24em; }
+      max-height: 24em;
+      max-width: 100%; }
     #converse-embedded-chat .chatbox .chat-body .chat-action,
     #conversejs .chatbox .chat-body .chat-action {
       font-style: italic; }

sass/_chatbox.scss

@@ -150,6 +150,7 @@
             }
             .chat-image {
                 max-height: 24em;
+                max-width: 100%;
             }
             .chat-action {
                 font-style: italic;