add warning for low fee

src/sass/views/includes/txp-details.scss

@@ -89,6 +89,17 @@
           flex-grow: 1;
         }
       }
+      &.low-fees {
+        border-top: none;
+        display: flex;
+        font-size: 14px;
+        color: #aaa;
+        align-items: center;
+        margin-top: -20px;
+        i {
+          padding-right: 20px;
+        }
+      }
     }
     .item-divider {
       padding-top: 1.2rem;

www/views/tx-details.html

@@ -84,6 +84,10 @@
             <span ng-if="toggleFeeFiat">{{feeFiatStr}}</span>
           </span>
         </div>
+        <div class="item low-fees" ng-if="btx.action == 'received' && btx.lowFees">
+          <i class="icon"><img src="img/icon-warning.png" width="20px"></i>
+          <span translate>This transaction could take a long time to confirm or could be dropped due to the low fees set by the sender</span>
+        </div>
         <div class="item single-line">
           <span class="label" translate>Confirmations</span>
           <span class="item-note">