feat(OHIFStandaloneViewer.js): adding NProgress loading bar on top of the page

package.json

@@ -82,6 +82,7 @@
     "@ohif/extension-dicom-pdf": "0.0.7",
     "@ohif/extension-vtk": "0.1.0",
     "@ohif/i18n": "0.1.0",
+    "@tanem/react-nprogress": "^1.1.25",
     "classnames": "^2.2.6",
     "cornerstone-core": "^2.2.8",
     "cornerstone-math": "^0.1.8",
@@ -103,6 +104,7 @@
     "react-resize-detector": "^4.2.0",
     "react-router": "^5.0.1",
     "react-router-dom": "^5.0.1",
+    "react-transition-group": "^4.1.1",
     "react-viewerbase": "0.12.0",
     "redux": "^4.0.1",
     "redux-logger": "^3.0.6",