Add documentation about Element X Android Gallery.

CONTRIBUTING.md

@@ -9,6 +9,7 @@
 * [Strings](#strings)
   * [I want to add new strings to the project](#i-want-to-add-new-strings-to-the-project)
   * [I want to help translating Element](#i-want-to-help-translating-element)
+  * [Element X Android Gallery](#element-x-android-gallery)
 * [I want to submit a PR to fix an issue](#i-want-to-submit-a-pr-to-fix-an-issue)
   * [Kotlin](#kotlin)
   * [Changelog](#changelog)
@@ -69,6 +70,14 @@ To help translating, please go to [https://localazy.com/p/element](https://local
 
 More information can be found [in this README.md](./tools/localazy/README.md).
 
+Once a language is sufficiently translated, it will be added to the app. The core team will decide when a language is sufficiently translated.
+
+### Element X Android Gallery
+
+Once added to Localazy, translations can be checked screen per screen using our tool Element X Android Gallery, available at https://element-hq.github.io/element-x-android/.
+
+Localazy syncs occur every Monday and the screenshots on this page are generated every Tuesday, so you'll have to wait to see your change appearing on Element X Android Gallery.
+
 ## I want to submit a PR to fix an issue
 
 Please have a look in the [dedicated documentation](./docs/pull_request.md) about pull request.

README.md

@@ -19,6 +19,7 @@ Learn more about why we are building Element X in our blog post: [https://elemen
 <!--- TOC -->
 
 * [Screenshots](#screenshots)
+* [Translations](#translations)
 * [Rust SDK](#rust-sdk)
 * [Status](#status)
 * [Contributing](#contributing)
@@ -50,6 +51,16 @@ adb shell am broadcast -a com.android.systemui.demo -e command exit
 |-|-|-|-|
 |<img src=./docs/images-lfs/screen_1_dark.png width=280 />|<img src=./docs/images-lfs/screen_2_dark.png width=280 />|<img src=./docs/images-lfs/screen_3_dark.png width=280 />|<img src=./docs/images-lfs/screen_4_dark.png width=280 />|
 
+## Translations
+
+Element X Android supports many languages. You can help us to translate the app in your language by joining our [Localazy project](https://localazy.com/p/element). You can also help us to improve the existing translations.
+
+Note that for now, we keep control on the French and German translations.
+
+Translations can be checked screen per screen using our tool Element X Android Gallery, available at https://element-hq.github.io/element-x-android/. Note that this page is updated every Tuesday. 
+
+More instructions about translating the application can be found at [CONTRIBUTING.md](CONTRIBUTING.md#strings).
+
 ## Rust SDK
 
 Element X leverages the [Matrix Rust SDK](https://github.com/matrix-org/matrix-rust-sdk) through an FFI layer that the final client can directly import and use.