Docs: Explain that the NDK is required

docs/content/en/docs/Getting started/_index.md

@@ -37,6 +37,9 @@ If you're wondering why so many packages are necessary, here's a quick overview
 - `moor_generator`: Generates query code based on your tables
 - `build_runner`: Common tool for code-generation, maintained by the Dart team
 
+Note that, on Android, the NDK is required. You can easily install the NDK and CMake from the SDK Manager in Android Studio
+by following the instructions [here](https://developer.android.com/studio/projects/install-ndk.md).
+
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 ### Declaring tables