Add drag/drop param loading.

Drop an image or generational text onto the prompt bar, it loads the info for parsing.

javascript/imageParams.js

@@ -0,0 +1,22 @@
+window.onload = (function(){
+    window.addEventListener('drop', e => {
+        const target = e.composedPath()[0];
+        const idx = selected_gallery_index();
+        let prompt_target = "txt2img_prompt_image";
+        if (idx === 1) {
+            prompt_target = "img2img_prompt_image";
+        }
+        if (target.placeholder === "Prompt") {
+            e.stopPropagation();
+            e.preventDefault();
+            const imgParent = gradioApp().getElementById(prompt_target);
+            const files = e.dataTransfer.files;
+            const fileInput = imgParent.querySelector('input[type="file"]');
+            if ( fileInput ) {
+                fileInput.files = files;
+                fileInput.dispatchEvent(new Event('change'));
+            }
+        }
+    });
+
+});