SUMMARY.md - Fix relative links being broken

Author: peter1745

public/mono-guide/src/SUMMARY.md

@@ -1,13 +1,13 @@
 # Summary
 
-- [Introduction](./introduction.md)
-	- [About Mono](./introduction/about-mono.md)
-	- [Building Mono](./introduction/building-mono.md)
-	- [Getting the Necessary Files](./introduction/necessary-files.md)
+- [Introduction](/introduction.md)
+	- [About Mono](/introduction/about-mono.md)
+	- [Building Mono](/introduction/building-mono.md)
+	- [Getting the Necessary Files](/introduction/necessary-files.md)
 
-- [First Steps](./first-steps/runtime-setup.md)
-	- [Loading Assemblies](./first-steps/loading-assemblies.md)
-	- [Testing Assembly Loading](./first-steps/testing-assembly-loading.md)
-	- [Classes](./first-steps/classes.md)
-	- [Methods](./first-steps/methods.md)
-	- [Fields and Properties](./first-steps/fields.md)
+- [First Steps](/first-steps/runtime-setup.md)
+	- [Loading Assemblies](/first-steps/loading-assemblies.md)
+	- [Testing Assembly Loading](/first-steps/testing-assembly-loading.md)
+	- [Classes](/first-steps/classes.md)
+	- [Methods](/first-steps/methods.md)
+	- [Fields and Properties](/first-steps/fields.md)