fix(welcome_page): Fix background image url path

css/_variables.scss

 $welcomePageBackground: none;
 $welcomePageTitleColor: #fff;
 
-$welcomePageHeaderBackground: linear-gradient(0deg, rgba(0, 0, 0, 0.2), rgba(0, 0, 0, 0.2)), url('/images/welcome-background.png');
+$welcomePageHeaderBackground: linear-gradient(0deg, rgba(0, 0, 0, 0.2), rgba(0, 0, 0, 0.2)), url('../images/welcome-background.png');
 $welcomePageHeaderBackgroundPosition: center;
 $welcomePageHeaderBackgroundRepeat: none;
 $welcomePageHeaderBackgroundSize: cover;