add button for languages setting

app/src/web/i18n.py

@@ -0,0 +1,32 @@
+from quart import Blueprint
+from quart import request, session, redirect
+from quart_babel import _
+
+
+LANGUAGES = {
+    'en': _('English'),
+    'de': _('German'),
+    'fr': _('French')
+}
+
+i18n_routes = Blueprint('i18n_routes', __name__)
+
+
+def my_get_locale():
+    try:
+        language = session['language']
+    except KeyError:
+        language = None
+    if language is not None:
+        return language
+
+    # check how to get the locale form for the add-on - hass.selectedLanguage
+    # logging.info("get_locale(%s)", request.accept_languages)
+    return request.accept_languages.best_match(LANGUAGES.keys())
+
+
+@i18n_routes.route('/language/<language>')
+def set_language(language=None):
+    if language in LANGUAGES:
+        session['language'] = language
+    return redirect(request.referrer)