Add file input for data reading

_assets/js/file_reader.js

@@ -0,0 +1,17 @@
+function getFileContents(file) {
+  var file = document.getElementById("fileUpload").files[0];
+  var fileContents = false;
+
+  if (file) {
+      var reader = new FileReader();
+      reader.readAsText(file, "UTF-8");
+      reader.onload = function (evt) {
+        var warData = JSON.parse(evt.target.result);
+        initApp(warData, 'withSave', warData);
+      }
+      reader.onerror = function (evt) {
+          console.error('error reading the file.')
+      }
+  }
+}
+