refactor JS

Rather than having all the JS all in one big file, separate the code into modules.

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

@@ -0,0 +1,27 @@
+const getImageHighlighterCallback = (id) => {
+    const imageHighlighter = document.getElementById(id);
+    imageHighlighter.onclick = () => {
+        imageHighlighter.childNodes.forEach((child) => {
+            child.classList.add('remove');
+            setTimeout(() => {
+                imageHighlighter.removeChild(child);
+            }, 100)
+        })
+    }
+
+    const imageHighlightCallback = (highlightEvent) => {
+        var bigImg = document.createElement('img');
+        bigImg.onclick = (imageClickEvent) => {
+            // This prevents the highlighter's onClick from closing the image when clicking on the image
+            // instead of next to it.
+            imageClickEvent.preventDefault();
+            imageClickEvent.stopPropagation();
+        };
+        bigImg.src = highlightEvent.target.src;
+        imageHighlighter.appendChild(bigImg);
+    };
+
+    return imageHighlightCallback
+}
+
+export default getImageHighlighterCallback;