add indication of upload error

web/static/editor.js

@@ -48,6 +48,10 @@ function addFileDrop(id) {
             textArea.classList.remove("drop-file-process")
         }).catch(err => {
             console.error(err);
+            textArea.classList.add("drop-file-error")
+            setTimeout(() => {
+                textArea.classList.remove("drop-file-error")
+            }, 2000)
         }).finally(() => {
             textArea.classList.remove("drop-file-process")
         })

web/static/style.css

@@ -50,3 +50,25 @@
     border-color: #5391ff;
     animation: border-pulsate 2s infinite;
 }
+
+
+@keyframes border-pulsate-error {
+    0% {
+        border-color: #ff3e3e;
+    }
+
+    50% {
+        border-color: rgba(0, 255, 255, 0);
+    }
+
+    100% {
+        border-color: #ff3e3e;
+    }
+}
+
+.drop-file-error {
+    border-style: solid;
+    border-width: 4px;
+    border-color: #ff3e3e;
+    animation: border-pulsate-error 1s 2;
+}