babel.cfg: ignore node_modules directories

The NPM packages contains python scripts: they should be included by "pybabel extract"

babel.cfg

@@ -1,3 +1,4 @@
+[ignore: **/node_modules/**]
 [python: **.py]
 [jinja2: **/templates/**.html]
 extensions=jinja2.ext.autoescape,jinja2.ext.with_