move jscript logic out of template/html, into jscript so we can keep all logic into the included file, then I can force version on it and stop caching issues in mobiles, and a shift-reload will also get new code, rather than a container restart even on desktops

internal/js/files_support.js

@@ -936,3 +936,21 @@ function goOutOfViewer()
     $('#viewer_div').addClass('d-none')
     $('#files_div').removeClass('d-none')
 }
+
+
+// left arrow onclick handler to go to prev image from inside the viewer
+function prevImageInViewer()
+{
+    getPreviousEntry()
+    setDisabledForViewingNextPrevBttons()
+    ViewImageOrVideo()
+}
+
+// right arrow onclick handler to go to next image from inside the viewer
+function nextImageInViewer()
+{
+    getNextEntry()
+    setDisabledForViewingNextPrevBttons()
+    ViewImageOrVideo()
+
+}