@merwok fix for content metadata key conflict

#96

Author: jzyinq

frontmatter/__init__.py

@@ -292,7 +292,7 @@ class Post(object):
     """
 
     def __init__(
-        self, content: str, handler: BaseHandler | None = None, **metadata: object
+        self, content: str, handler: BaseHandler | None = None, /, **metadata: object
     ) -> None:
         self.content = str(content)
         self.metadata = metadata