add imgInput element with eveneListener for uploading image

backstage/static/js/blockElements.js

@@ -41,6 +41,18 @@ function getImgElements(blockDiv) {
   const imgDiv = document.createElement("div");
   const img = document.createElement("img");
   const imgInput = document.createElement("INPUT");
+  imgInput.setAttribute("type", "file");
+  imgInput.addEventListener('change', function(event) {
+    if (event.target.files[0]) {
+      let formData = new FormData();
+      formData.append('image', event.target.files[0])
+      axios.post('http://127.0.0.1:5000/api/upload/img?url=/家具規劃作品/公仔與爵士鼓', formData, {
+        headers: {
+        'Content-Type': 'multipart/form-data'
+        }
+      })
+    }
+  });
   const widthInput = document.createElement("INPUT");
   const heightInput = document.createElement("INPUT");
   const imgInputButton = document.createElement('button');