[ModelicaSystem] add docstring

Author: syntron

OMPython/ModelicaSystem.py

@@ -319,6 +319,10 @@ def parse_simflags(simflags: str) -> dict[str, Optional[str | dict[str, Any] | n
 
 
 class ModelicaSystem:
+    """
+    Class to run OpenModelica simulations.
+    """
+
     def __init__(
             self,
             fileName: Optional[str | os.PathLike] = None,