add check for directory in config loader

src/dopt_basics/configs.py

@@ -14,6 +14,9 @@ def load_toml(
 
     if not path_to_toml.exists():
         raise FileNotFoundError(f"Config file seems not to exist under: >{path_to_toml}<")
+    if not path_to_toml.is_file():
+        raise ValueError("Object to which path points must be a file.")
+
     path_to_toml = path_to_toml.with_suffix(".toml")
 
     with open(path_to_toml, "rb") as f: