[ModelicaSystem] add docstring

Author: syntron

OMPython/ModelicaSystem.py

@@ -323,6 +323,10 @@ def parse_simflags(simflags: str) -> dict[str, Optional[str | dict[str, Any] | n
 
 
 class ModelicaSystem:
+    """
+    Class to run OpenModelica simulations.
+    """
+
     def __init__(
             self,
             commandLineOptions: Optional[list[str]] = None,