BMI calculator example (#130)

bmi_calculator/lib/body_model.dart

@@ -0,0 +1,19 @@
+enum Sex {
+  male,
+  female,
+}
+
+// User body model class
+class BodyModel {
+  Sex sex;
+  int height;
+  int weight;
+  int age;
+
+  BodyModel({
+    required this.sex,
+    required this.height,
+    required this.weight,
+    required this.age,
+  });
+}