text: Title: Getting AggGrid's state
  Body: Hey @PablocFonseca, thank you for such an amazing job on integrating AggGrid in Streamlit, I highly appreciate the efforts and happy to contribute if there are any known issues that need help from python side of things.
  
  One task I am having hard time to wrap my head around is getting AggGrid state after a user interacts with it. 
  
  I.e., I have a multi-select to keep grouping consistent between page reloads or new data push.
  ```
  # let user pick cols from dataframe she want to group by
  if st.sidebar.checkbox("Enable default grouping"):
      default_group_col = st.sidebar.selectbox("Default group by: ", cols, 1)
  
  # if any of columns are selected, apply it to aggrid and persist on page reload,
  # as default_group_col state is persisted under the hood by streamlit
  try:
      gb.configure_column(default_group_col, rowGroup=True)
  except:
      pass
  ```
  
  Now say a user groups by an additional column using AggGrid groupby feature, collapses some of the resulting groups and keeps the others expanded. I would assume AggGrid itself stores this state somewhere in client side JS. Is there a potential way to get stat state back to python in order to save it somewhere in a dict and persist between page reloads when AggGrid component is being redrawn or populated with new data?
  
  Thanks!