make the templates dir more reliable

changedetectionio/flask_app.py

@@ -813,7 +813,9 @@ def changedetection_app(config=None, datastore_o=None):
                 # So that the extra panels can access _helpers.html etc, we set the environment to load from templates/
                 # And then render the code from the module
                 from jinja2 import Environment, FileSystemLoader
-                env = Environment(loader=FileSystemLoader('templates'))
+                import importlib.resources
+                templates_dir = str(importlib.resources.files("changedetectionio").joinpath('templates'))
+                env = Environment(loader=FileSystemLoader(templates_dir))
                 template = env.from_string(form.extra_form_content())
                 included_content = template.render(**template_args)