Import custom styles last

To make sure that custom styles are preferred to default styles, import
them as the last module.

Author: PeeterPaal

sources/stylesheets/main.scss

@@ -6,8 +6,6 @@
 @import 'components/header';
 @import 'components/search';
 
-@import 'custom-styles/main-styles.scss';
-
 @import 'layouts/auto-generated-product';
 @import 'layouts/common-page';
 @import 'layouts/front-page';
@@ -20,3 +18,5 @@
 @import 'content-formatted';
 @import 'fonts';
 @import 'general';
+
+@import 'custom-styles/main-styles.scss';