add new viewer folder

OHIFViewer-react/src/App.css

@@ -0,0 +1,16 @@
+html,
+body,
+#root {
+  background-color: black;
+  height: 100%;
+  width: 100%;
+  margin: 0;
+}
+
+body {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}