Split config lines on the first equal sign (#504)

sgpt/config.py

@@ -75,7 +75,7 @@ def _read(self) -> None:
         with open(self.config_path, "r", encoding="utf-8") as file:
             for line in file:
                 if line.strip() and not line.startswith("#"):
-                    key, value = line.strip().split("=")
+                    key, value = line.strip().split("=", 1)
                     self[key] = value
 
     def get(self, key: str) -> str:  # type: ignore