Changes to fileInput accessibility and fix to prevent jumping around the page on activation

inst/js/a11yShinyInputs.js

@@ -11,4 +11,13 @@ const clearAll = function(event) {
   $input.find('input[type=\"checkbox\"]').prop('checked', false);
   $input.trigger('change');
   return false;
-};
+};
+const fileInputClick = function(event) {
+  $('#' + $(event.target).data('target')).click();
+}
+const fileInputKeydown = function(event) {
+  if (event.key == "Enter" || event.key == " ") {
+    event.preventDefault();
+    $('#' + $(event.target).data('target')).click();
+  }
+}