Added basic welcome screen

lib/screens/welcome.dart

@@ -0,0 +1,146 @@
+import 'package:flutter/material.dart';
+import 'package:routemaster/routemaster.dart';
+import 'package:flutter_svg/flutter_svg.dart';
+import 'dart:math';
+
+class WelcomePage extends StatefulWidget {
+  const WelcomePage({super.key});
+
+  @override
+  State<WelcomePage> createState() => _WelcomePageState();
+}
+
+class _WelcomePageState extends State<WelcomePage> {
+  final PageController controller = PageController();
+  int _currentPage = 0;
+
+  @override
+  void initState() {
+    super.initState();
+
+    _currentPage = controller.initialPage;
+    controller.addListener(() {
+        setState(() {
+            _currentPage = controller.page?.toInt() ?? controller.initialPage;
+        });
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final textTheme = Theme.of(context)
+    .textTheme
+    .apply(displayColor: Theme.of(context).colorScheme.onSurface);
+
+    String fabText = "Next";
+    if (_currentPage == 0) {
+      fabText = "Let's go";
+    } else if (_currentPage == 4 - 1) {
+      fabText = "Sign up";
+    }
+
+    double width = MediaQuery.of(context).size.width;
+    double height = MediaQuery.of(context).size.height;
+
+    double smallest = min(width, height);
+
+    return Scaffold(
+      body: Column(
+        children: [
+          Expanded(
+            child: PageView(
+              controller: controller,
+              children: <Widget>[
+                Column(
+                  mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: <Widget>[
+                    SvgPicture.asset("undraw/undraw_shopping_app.svg",
+                      fit: BoxFit.contain,
+                      width: smallest*0.5,
+                      height: smallest*0.5
+                    ),
+                    Text(
+                      'Welcome to Outbag',
+                      style: textTheme.displaySmall,
+                    ),
+                    Text('Shopping lists made easy', style: textTheme.bodyMedium)
+                  ],
+                ),
+                Column(
+                  mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: <Widget>[
+                    SvgPicture.asset("undraw/undraw_mobile_login.svg",
+                      fit: BoxFit.contain,
+                      width: smallest*0.5,
+                      height: smallest*0.5),
+                    Text(
+                      'Open. Decentralized',
+                      style: textTheme.displaySmall,
+                    ),
+                    Text('One account, multiple servers',
+                      style: textTheme.bodyMedium)
+                  ],
+                ),
+                Column(
+                  mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: <Widget>[
+                    SvgPicture.asset("undraw/undraw_online_connection.svg",
+                      fit: BoxFit.contain,
+                      width: smallest*0.5,
+                      height: smallest*0.5),
+                    Text(
+                      'Made to share',
+                      style: textTheme.displaySmall,
+                    ),
+                    Text('Collaborate on your shopping list in real time',
+                      style: textTheme.bodyMedium)
+                  ],
+                ),
+                Column(
+                  mainAxisAlignment: MainAxisAlignment.center,
+                  crossAxisAlignment: CrossAxisAlignment.center,
+                  children: <Widget>[
+                    SvgPicture.asset("undraw/undraw_online_groceries.svg",
+                      fit: BoxFit.contain,
+                      width: smallest*0.5,
+                      height: smallest*0.5),
+                    Text(
+                      'Pocket-sized',
+                      style: textTheme.displaySmall,
+                    ),
+                    Text('Always have your shopping list with you',
+                      style: textTheme.bodyMedium)
+                  ],
+                ),
+              ],
+          )),
+          TextButton(
+            onPressed: () {
+              Routemaster.of(context).push("/signin");
+            },
+            child: const Text('I already have an account'),
+          )
+        ],
+      ),
+      floatingActionButton: FloatingActionButton.extended(
+        icon: const Icon(Icons.chevron_right),
+        label: Text(fabText),
+        tooltip: 'Continue tour',
+        onPressed: () {
+          if (controller.page == 4 - 1) {
+            // open signup screen
+            Routemaster.of(context).push("/signup");
+          } else {
+            // move to next page
+            controller.nextPage(
+              curve: Curves.easeInOut,
+              duration: const Duration(milliseconds: 300));
+          }
+        },
+      ),
+    );
+  }
+}