docs: initial content for Adding Native Code (#24)

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

Author: 3 people

content/guide/adding-native-code.md

@@ -0,0 +1,32 @@
+---
+title: Adding custom native code to a project
+---
+
+
+NativeScript allows you to access any native APIs anytime in your app. If the native API you need is not exposed through [@nativescript/core](https://docs.nativescript.org/understanding-packages#nativescript-core) or [third party plugins](https://market.nativescript.org/) or [@nativescript/* plugins](https://docs.nativescript.org/plugins/index.html)), you can add it to your project and access it right away in TypeScript.
+
+
+1. Add native code to [App_Resources](/project-structure/app-resources). For example, see [Adding Java/Kotlin code to an application](/project-structure/app-resources#adding-java-kotlin-code-to-an-application) and [Adding ObjectiveC/Swift Code to an application](/project-structure/app-resources#adding-objectivec-swift-code-to-an-application)
+
+2. Generate types for the added APIs
+For iOS types run:
+
+```cli
+ns typings ios
+```
+
+For Android run:
+
+```cli
+ns typings android --jar <.jar path>
+```
+
+3. Reference the generated types in [references.d.ts](/project-structure/references-d-ts-in-nativescript)
+
+4. You can now code (_strongly typed_) against the platform native APIs. For various examples on how to interact with native API's in JavaScript/TypeScript, visit the [Subclassing](/guide/subclassing/), [iOS Marshalling](/guide/marshalling/nativescript-ios-marshalling) and [Android Marshalling](/guide/marshalling/nativescript-android-marshalling) pages
+
+:::details Additional Resources
+
+- [Android d.ts Generator](https://github.com/NativeScript/android-dts-generator), for advanced types generation for Android
+
+:::

content/sidebar.ts

@@ -220,6 +220,10 @@ export default [
   {
     text: 'Advanced Concepts',
     items: [
+      {
+        text: 'Adding Native Code',
+        link: '/guide/adding-native-code'
+      },
       {
         text: 'Data Binding',
         link: '/guide/data-binding',