appgenerator : Readme + compile .po/.mo (#2276)

* appgenerator: add README.md

* appgenerator: compile .po/.mo

tools/app_generator/README.md

@@ -0,0 +1,42 @@
+# YunoHost app generator
+
+This is a Flask app generating a draft .zip of a YunoHost application after filling a form
+
+## Developement
+
+```bash
+python3 -m venv venv
+source venv/bin/activate
+pip3 install -r requirements.txt
+
+# you need to manually download the assets to have access to the css and the javascript files
+(cd assets && bash fetch_assets)
+```
+
+And then start the dev server:
+
+```bash
+source venv/bin/activate
+FLASK_APP=app.py FLASK_ENV=development flask --debug run
+```
+
+## Translation
+
+It's based on Flask-Babel : <https://python-babel.github.io/flask-babel/>
+
+```bash
+source venv/bin/activate
+
+# Extract the english sentences from the code, needed if you modified it
+pybabel extract --ignore-dirs venv -F babel.cfg -o messages.pot .
+
+# If working on a new locale: initialize it (in this example: fr)
+pybabel init -i messages.pot -d translations -l fr
+# Otherwise, update the existing .po:
+pybabel update -i messages.pot -d translations
+
+# ... translate stuff in translations/<lang>/LC_MESSAGES/messages.po
+# re-run the 'update' command to let Babel properly format the text
+# then compile:
+pybabel compile -d translations
+```