Improve styles for ConversationListItem

- Display last message
- Fix user talking to themself

Change-Id: Ia5bb3f9cd86a389f94bbfb3e279e7a82878f98ed
diff --git a/client/src/themes/Default.ts b/client/src/themes/Default.ts
index a3f1b86..a29c68d 100644
--- a/client/src/themes/Default.ts
+++ b/client/src/themes/Default.ts
@@ -392,6 +392,24 @@
           },
         },
       },
+      MuiListItemButton: {
+        styleOverrides: {
+          root: {
+            '&.Mui-selected': {
+              backgroundColor: '#cccccc',
+              opacity: 1,
+              '&:hover': {
+                backgroundColor: '#cccccc',
+                opacity: 1,
+              },
+            },
+            '&:hover': {
+              backgroundColor: '#d5d5d5',
+              opacity: 1,
+            },
+          },
+        },
+      },
     },
   });
 };