Add deploy agent environment example

deploy/deploy-agent/.env.example

@@ -0,0 +1,5 @@
+FRONTEND_DEPLOY_BRANCH=main
+FRONTEND_DEPLOY_SOURCE_PATH=/opt/raspi-chat/source
+FRONTEND_DEPLOY_ADMIN_WEBROOT=/var/www/example_user/data/www/admin.example.ru
+FRONTEND_DEPLOY_WIDGET_WEBROOT=/var/www/example_user/data/www/widget.example.ru
+FASTPANEL_SAFE_MODE=true