fix(init): class attribute has t be defined also at init level

Author: Guts

mkdocs_rss_plugin/plugin.py

@@ -60,6 +60,8 @@ def __init__(self, *args, **kwargs):
         # pages storage
         super().__init__(*args, **kwargs)
 
+        self.cmd_is_serve: bool = False
+
     def on_startup(
         self, *, command: Literal["build", "gh-deploy", "serve"], dirty: bool
     ) -> None: