[firebase_in_app_messaging] add firebase_in_app_messaging in README (#1875)

* add firebase_in_app_messaging in README

* Update FlutterFire.md

* Update CODEOWNERS
diff --git a/CODEOWNERS b/CODEOWNERS
index a5c22c9..802ffe4 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -18,6 +18,7 @@
 packages/firebase_crashlytics/* @kroikie @collinjackson
 packages/firebase_database/* @collinjackson @kroikie
 packages/firebase_dynamic_links/* @bparrishMines
+packages/firebase_in_app_messaging/* @collinjackson
 packages/firebase_messaging/* @collinjackson @kroikie
 packages/firebase_ml_vision/* @bparrishMines
 packages/firebase_performance/* @bparrishMines @collinjackson
diff --git a/FlutterFire.md b/FlutterFire.md
index aaff762..ae039e6 100644
--- a/FlutterFire.md
+++ b/FlutterFire.md
@@ -23,6 +23,7 @@
 | [firebase_crashlytics][crash_pub] | ![pub package][crash_badge] | [Firebase Crashlytics][crash_product] | [`packages/firebase_crashlytics`][crash_code] |
 | [firebase_database][database_pub] | ![pub package][database_badge] | [Firebase Realtime Database][database_product] | [`packages/firebase_database`][database_code] |
 | [firebase_dynamic_links][dynamic_links_pub] | ![pub package][dynamic_links_badge] | [Firebase Dynamic Links][dynamic_links_product] | [`packages/firebase_dynamic_links`][dynamic_links_code] |
+| [in_app_messaging][in_app_messaging_pub] | ![pub package][in_app_messaging_badge] | [Firebase In-App Messaging][in_app_messaging_product] | [`packages/firebase_in_app_messaging`][in_app_messaging_code] |
 | [firebase_messaging][messaging_pub] | ![pub package][messaging_badge] | [Firebase Cloud Messaging][messaging_product] | [`packages/firebase_messaging`][messaging_code] |
 | [firebase_ml_vision][ml_vision_pub] | ![pub package][ml_vision_badge] | [Firebase ML Kit][ml_vision_product] | [`packages/firebase_ml_vision`][ml_vision_code] |
 | [firebase_performance][performance_pub] | ![pub package][performance_badge] | [Firebase Performance Monitoring][performance_product] | [`packages/firebase_performance`][performance_code] |
@@ -74,6 +75,11 @@
 [functions_code]: https://github.com/flutter/plugins/tree/master/packages/cloud_functions
 [functions_badge]: https://img.shields.io/pub/v/cloud_functions.svg
 
+[in_app_messaging_pub]: https://pub.dartlang.org/packages/firebase_in_app_messaging
+[in_app_messaging_product]: https://firebase.google.com/products/in-app-messaging/
+[in_app_messaging_code]: https://github.com/flutter/plugins/tree/master/packages/firebase_in_app_messaging
+[in_app_messaging_badge]: https://img.shields.io/pub/v/firebase_in_app_messaging.svg
+
 [messaging_pub]: https://pub.dartlang.org/packages/firebase_messaging
 [messaging_product]: https://firebase.google.com/products/cloud-messaging/
 [messaging_code]: https://github.com/flutter/plugins/tree/master/packages/firebase_messaging
diff --git a/README.md b/README.md
index 514814a..f6695a7 100644
--- a/README.md
+++ b/README.md
@@ -69,6 +69,7 @@
 | [firebase_crashlytics](./packages/firebase_crashlytics/) | [![pub package](https://img.shields.io/pub/v/firebase_crashlytics.svg)](https://pub.dev/packages/firebase_crashlytics) |
 | [firebase_database](./packages/firebase_database/) | [![pub package](https://img.shields.io/pub/v/firebase_database.svg)](https://pub.dev/packages/firebase_database) |
 | [firebase_dynamic_links](./packages/firebase_dynamic_links/) | [![pub package](https://img.shields.io/pub/v/firebase_dynamic_links.svg)](https://pub.dev/packages/firebase_dynamic_links) |
+| [firebase_in_app_messaging](./packages/firebase_in_app_messaging/) | [![pub package](https://img.shields.io/pub/v/firebase_in_app_messaging.svg)](https://pub.dev/packages/firebase_in_app_messaging) |
 | [firebase_messaging](./packages/firebase_messaging/) | [![pub package](https://img.shields.io/pub/v/firebase_messaging.svg)](https://pub.dev/packages/firebase_messaging) |
 | [firebase_ml_vision](./packages/firebase_ml_vision/) | [![pub package](https://img.shields.io/pub/v/firebase_ml_vision.svg)](https://pub.dev/packages/firebase_ml_vision) |
 | [firebase_performance](./packages/firebase_performance/) | [![pub package](https://img.shields.io/pub/v/firebase_performance.svg)](https://pub.dev/packages/firebase_performance) |