Added IBM Plex sans as custom font, added more properties to the gradient button

lib/src/App.dart

@@ -9,6 +9,7 @@ class App extends StatelessWidget {
       home: LoginScreen(),
       theme: ThemeData(
         canvasColor: Color.fromRGBO(23, 25, 29, 1.0),
+        fontFamily: 'IBM Plex Sans',
       ),
     );
   }

lib/src/screens/login_screen.dart

@@ -14,11 +14,20 @@ class LoginScreen extends StatelessWidget {
               child: Center(
                 child: Logo(),
               ),
-              flex: 4,
+              flex: 3,
             ),
             Expanded(
               child: Center(
-                child: GradientButton(),
+                child: GradientButton(
+                  child: Text(
+                    'LOGIN',
+                    style: TextStyle(
+                      color: Colors.white,
+                      fontSize: 15,
+                      fontWeight: FontWeight.w600,
+                    ),
+                  ),
+                ),
               ),
               flex: 1,
             ),

lib/src/widgets/gradient_button.dart

@@ -1,17 +1,33 @@
+import 'dart:math';
+
 import 'package:flutter/material.dart';
 
 class GradientButton extends StatelessWidget {
+  final double radius;
+  final Widget child;
+  final double height;
+  final double width;
+  GradientButton({
+    this.radius = 4,
+    @required this.child,
+    this.height,
+    this.width,
+  });
+
   Widget build(BuildContext context) {
     return ConstrainedBox(
       constraints: const BoxConstraints(minWidth: 88.0, minHeight: 36.0),
       child: Container(
+        width: width,
+        height: height,
         padding: EdgeInsets.all(5),
         child: Center(
           widthFactor: 1.0,
           heightFactor: 1.0,
-          child: Text('My custom Button'),
+          child: child,
         ),
         decoration: BoxDecoration(
+          borderRadius: BorderRadius.circular(radius),
           gradient: LinearGradient(
               begin: Alignment.topLeft,
               end: Alignment.bottomRight,