docs: Fix link

Author: johannes-wolf

docs/basics/custom-types.mdx

@@ -9,7 +9,7 @@ Many CeTZ functions expect data in certain formats which we will call types. Not
 
 ## <Type>coordinate</Type>
 
-A position on the canvas specified by any coordinate system. See [Coordinate Systems](../coordinate-systems).
+A position on the canvas specified by any coordinate system. See [Coordinate Systems](/basics/coordinate-systems).
 
 ## <Type>number</Type>