add fileInput widget to multiSelect

src/main/resources/static/js/multitool/fileInput.js

@@ -0,0 +1,69 @@
+const addFileDragListener = (callback) => {
+    let overlay;
+    let dragCounter = 0;
+
+    const dragenterListener = function() {
+        dragCounter++;
+        if (!overlay) {
+            // Create and show the overlay
+            overlay = document.createElement('div');
+            overlay.style.position = 'fixed';
+            overlay.style.top = 0;
+            overlay.style.left = 0;
+            overlay.style.width = '100%';
+            overlay.style.height = '100%';
+            overlay.style.background = 'rgba(0, 0, 0, 0.5)';
+            overlay.style.color = '#fff';
+            overlay.style.zIndex = '1000';
+            overlay.style.display = 'flex';
+            overlay.style.alignItems = 'center';
+            overlay.style.justifyContent = 'center';
+            overlay.style.pointerEvents = 'none';
+            overlay.innerHTML = '<p>Drop files anywhere to upload</p>';
+            document.getElementById('content-wrap').appendChild(overlay);
+        }
+    };
+
+    const dragleaveListener = function() {
+        dragCounter--;
+        if (dragCounter === 0) {
+            // Hide and remove the overlay
+            if (overlay) {
+                overlay.remove();
+                overlay = null;
+            }
+        }
+    };
+
+    const dropListener = function(e) {
+
+        const dt = e.dataTransfer;
+        const files = dt.files;
+        callback(files).catch((err) => {
+            console.error(err);
+            //maybe
+        }).finally(() => {
+            if (overlay) {
+                overlay.remove();
+                overlay = null;
+            }
+        });
+    };
+
+    // Prevent default behavior for drag events
+    ['dragenter', 'dragover', 'dragleave', 'drop'].forEach(eventName => {
+        document.body.addEventListener(eventName, preventDefaults, false);
+    });
+
+    function preventDefaults(e) {
+        e.preventDefault();
+        e.stopPropagation();
+    }
+
+    document.body.addEventListener('dragenter', dragenterListener);
+    document.body.addEventListener('dragleave', dragleaveListener);
+    // Add drop event listener
+    document.body.addEventListener('drop', dropListener);
+}
+
+export default addFileDragListener;