Add real docs

Author: samtstern

docs/README.md

@@ -20,7 +20,11 @@ visit the [main README][main-readme].
 
 ## Kotlin Extensions
 
+The following Firebase SDKs for Android have Kotlin extension libraries
+that allow you to write more idiomatic Kotlin code when using Firebase
+in your app:
 
+  * [`firebase-firestore`](./ktx/firestore.md)
 
 [android-setup]: https://firebase.google.com/docs/android/setup
 [main-readme]: https://github.com/firebase/firebase-android-sdk/blob/master/README.md

docs/ktx/firestore.md

@@ -1,5 +1,67 @@
 # Firestore Kotlin Extensions
 
+## Getting Started
+
+To use the Cloud Firestore Android SDK with Kotlin Extenstions, add the following
+to your app's `build.gradle` file:
+
+```groovy
+// This library transitively includes the Firestore Android SDK
+implementation 'com.google.firebase:firebase-firestore-ktx:18.1.0
+```
+
+## Features
+
+### Convert a DocumentSnapshot field to a POJO
+
+**Kotlin**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get("fieldPath", MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.get<MyClass>("fieldPath")
+```
+
+### Get an instance of FirebaseFirestore
+
+**Kotlin**
+```kotlin
+val firestore = FirebaseFirestore.getInstance()
 ```
-// TODO: Finish this page
+
+**Kotlin + KTX**
+```kotlin
+val firestore = Firebase.firestore
+```
+
+### Convert a DocumentSnapshot to a POJO
+
+**Kotlin**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.toObject(MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: DocumentSnapshot = ...
+val myObject = snapshot.toObject<MyClass>()
+```
+
+### Convert a QuerySnapshot to a list of POJOs
+
+**Kotlin**
+```kotlin
+val snapshot: QuerySnapshot = ...
+val objectList = snapshot.toObjects(MyClass::class.java)
+```
+
+**Kotlin + KTX**
+```kotlin
+val snapshot: QuerySnapshot = ...
+val objectList = snapshot.toObjects<MyClass>()
 ```