add styleguide

docs/index.md

@@ -6,6 +6,7 @@ Aktuell findet Ihr hier:
 
 * [Maps Tutorial](maps.md)
 * [HowTo Play](play.md)
+* [Design/Styleguide](https://style.rc3.world)
 
 This pages should give you an overview over rC3 2021, connected services, as well
 as how to contribute to rC3.
@@ -14,6 +15,7 @@ For now, you can find the following here:
 
 * [Maps Tutorial](maps.en.md)
 * [HowTo Play](play.en.md)
+* [Design/Styleguide](https://style.rc3.world)
 
 
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