Added covid-19 example app and Updated the readme (#73)

covid19_mobile_app/lib/widgets/foldable_cell_widgets.dart

@@ -0,0 +1,143 @@
+import 'package:flutter/material.dart';
+import 'package:folding_cell/folding_cell.dart';
+import 'package:number_display/number_display.dart';
+
+// To display data in a width-limited component
+// Eg: converts 2,000,000 to 2M
+String updateNumberDisplay(String number) {
+  final display = createDisplay(length: 4);
+  // we are converting number to an integer because it is a string
+  // and display expects an integer
+  return display(int.parse(number));
+}
+
+// the front widget for the foldable cell(when cell is collapsed)
+Widget buildFrontWidget(
+    BuildContext context, String flagUrl, String country, String cases) {
+  return Padding(
+    padding: const EdgeInsets.symmetric(horizontal: 16.0),
+    child: Row(
+      children: <Widget>[
+        Container(
+            child: Image.network(
+          flagUrl,
+          width: MediaQuery.of(context).size.width * 0.2,
+          fit: BoxFit.cover,
+        )),
+        SizedBox(
+          width: 20.0,
+        ),
+        Expanded(
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: <Widget>[
+              Text(
+                "Country: $country",
+              ),
+              Text("Total Cases: ${updateNumberDisplay(cases)}"),
+            ],
+          ),
+        ),
+      ],
+    ),
+  );
+}
+
+// the inner top widget for the foldable cell(when cell is expanded)
+Widget buildInnerTopWidget(String country, String todayCases, String deaths,
+    String todayDeaths, String recovered, String critical, String cpm) {
+  return Container(
+    padding: const EdgeInsets.symmetric(horizontal: 10.0),
+    color: Color(0xfff44e3f),
+    child: Column(
+      mainAxisAlignment: MainAxisAlignment.start,
+      children: <Widget>[
+        Text(
+          country,
+          style: TextStyle(fontSize: 20.0),
+        ),
+        SizedBox(
+          height: 10.0,
+        ),
+        Row(
+          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+          children: <Widget>[
+            Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: <Widget>[
+                Text(
+                  "Today Cases: ${updateNumberDisplay(todayCases)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+                Text(
+                  "Deaths: ${updateNumberDisplay(deaths)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+                Text(
+                  "Cases/Million: ${updateNumberDisplay(cpm)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+              ],
+            ),
+            SizedBox(
+              width: 10.0,
+            ),
+            Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: <Widget>[
+                Text(
+                  "Recovered: ${updateNumberDisplay(recovered)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+                Text(
+                  "Today Deaths: ${updateNumberDisplay(todayDeaths)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+                Text(
+                  "Critical: ${updateNumberDisplay(critical)}",
+                  style: TextStyle(fontSize: 18.0),
+                ),
+              ],
+            ),
+          ],
+        ),
+      ],
+    ),
+  );
+}
+
+// the inner bottom widget for the foldable cell(when cell is expanded)
+Widget buildInnerBottomWidget(String cases) {
+  return Builder(builder: (context) {
+    return Container(
+      color: Color(0xfff44e3f),
+      padding: EdgeInsets.all(8.0),
+      child: Column(
+        children: <Widget>[
+          Expanded(
+              child: Text(
+            "Total Cases:\n${updateNumberDisplay(cases)}",
+            textAlign: TextAlign.center,
+            style: TextStyle(
+              fontSize: 20.0,
+            ),
+          )),
+          FlatButton(
+            onPressed: () {
+              SimpleFoldingCellState foldingCellState =
+                  context.findAncestorStateOfType();
+              foldingCellState?.toggleFold();
+            },
+            child: Text(
+              "Close",
+            ),
+            color: Colors.black,
+            shape: StadiumBorder(),
+            splashColor: Colors.white.withOpacity(0.5),
+          ),
+        ],
+      ),
+    );
+  });
+}