Create an Architecture doc

Add translation info

Author: Renarde-dev

docs/Architecture.md

@@ -0,0 +1,23 @@
+# Architecture :
+
+This file document the different directory of this project.
+Each section will contain explanation and a directory tree.
+
+## Translations :
+
+Translations are hosted on [crowdin](https://crowdin.com/project/piwigo-ng), everything is translated from english.  
+Flutter take the `app_%%.arb` files and generate dart code inside the `lib/l10n` directory.   
+
+```sh
+# %% = country code
+.
+├── crowdin.yml
+├── l10n
+│  ├── app_en.arb
+│  ├── app_%%.arb
+│  └── untranslated.json
+└── l10n.yaml
+   └── l10n
+      ├── app_localizations.dart
+      └── app_localizations_%%.dart
+```