refactor: Switch to flutter_lints

lib/widgets/layouts/loading_view.dart

@@ -5,6 +5,8 @@ import 'package:fluffychat/widgets/matrix.dart';
 import 'package:flutter/material.dart';
 
 class LoadingView extends StatelessWidget {
+  const LoadingView({Key key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     if (Matrix.of(context)
@@ -23,6 +25,6 @@ class LoadingView extends StatelessWidget {
         ),
       );
     }
-    return EmptyPage(loading: true);
+    return const EmptyPage(loading: true);
   }
 }

lib/widgets/layouts/max_width_body.dart

@@ -22,7 +22,7 @@ class MaxWidthBody extends StatelessWidget {
         );
         return withScrolling
             ? SingleChildScrollView(
-                physics: ScrollPhysics(),
+                physics: const ScrollPhysics(),
                 child: Padding(
                   padding: padding,
                   child: child,

lib/widgets/layouts/one_page_card.dart

@@ -17,7 +17,7 @@ class OnePageCard extends StatelessWidget {
             Matrix.of(context).client.isLogged()
         ? child
         : Container(
-            decoration: BoxDecoration(
+            decoration: const BoxDecoration(
               image: DecorationImage(
                 image: AssetImage('assets/login_wallpaper.jpg'),
                 fit: BoxFit.cover,

lib/widgets/layouts/side_view_layout.dart

@@ -28,9 +28,9 @@ class SideViewLayout extends StatelessWidget {
                     color: Theme.of(context).dividerColor,
                   ),
                   AnimatedContainer(
-                    duration: Duration(milliseconds: 300),
+                    duration: const Duration(milliseconds: 300),
                     clipBehavior: Clip.antiAlias,
-                    decoration: BoxDecoration(),
+                    decoration: const BoxDecoration(),
                     width: hideSideView ? 0 : 360.0,
                     child: hideSideView ? null : sideView,
                   ),

lib/widgets/layouts/two_column_layout.dart

@@ -19,7 +19,7 @@ class TwoColumnLayout extends StatelessWidget {
           children: [
             Container(
               clipBehavior: Clip.antiAlias,
-              decoration: BoxDecoration(),
+              decoration: const BoxDecoration(),
               width: 360.0,
               child: mainView,
             ),