First draft of Onboarding page

lib/core/const/text_constants.dart

@@ -0,0 +1,12 @@
+class TextConstants {
+  // Onboarding
+  static const String onboarding1Title = "Workout anywhere";
+  static const String onboardingTitle = "Learn techniques";
+  static const String onboarding3Title = "Stay strong & healthy";
+  static const String onboardingDescription =
+  "You can do your workout at home without any equipment, outside or at the gym.";
+  static const String onboarding2Description =
+      "Our workout programs are made by professionals.";
+  static const String onboarding3Description =
+      "We want you to fully enjoy the program and stay healthy and positive.";
+}