docs: initial content for Marshalling index (#30)

Co-authored-by: Nathan Walker <[email protected]>

Author: Ombuweb

content/guide/marshalling/index.md

@@ -0,0 +1,12 @@
+---
+title: Marshalling in NativeScript
+---
+
+Marshalling in NativeScript refers to the conversion of JavaScript data types to native platform language (Swift/Objective C and Kotlin/Java) data types and vice versa.
+
+The conversion is handled implicitly by the NativeScript iOS and Android runtimes.
+
+For more information about how NativeScript converts data types for each platform, read the following articles:
+
+- [iOS Marshalling](/guide/marshalling/nativescript-ios-marshalling)
+- [Android Marshalling](/guide/marshalling/nativescript-android-marshalling)

content/sidebar.ts

@@ -252,7 +252,7 @@ export default [
       },
       {
         text: 'Marshalling',
-        link: '#',
+        link: '/guide/marshalling',
         items: [
           {
             text: 'iOS Marshalling',