Show email signature with maximum height 8vh, fixes #4021 (#4063)

Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>
Co-authored-by: Fayaz Ahmed <15716057+fayazara@users.noreply.github.com>
Co-authored-by: Nithin David Thomas <1277421+nithindavid@users.noreply.github.com>

app/javascript/dashboard/components/widgets/conversation/ReplyBox.vue

@@ -700,6 +700,8 @@ export default {
   justify-content: space-between;
   border: 1px dashed var(--s-100);
   border-radius: var(--border-radius-small);
+  max-height: 8vh;
+  overflow: auto;
 
   &:hover {
     background: var(--s-25);