Typo dispaly_input_row and code improvement

[umazel]

Link to doc page in question (if any):
https://docs.streamlit.io/develop/concepts/design/buttons

Name of the Streamlit feature whose docs need improvement:
Button behavior and examples

What you think the docs should say:

Buttons to add other widgets dynamically
change: from dispaly_input_row to display_input_row
reason: wrong spelling

Buttons to handle expensive or file-writing processes
change: from st.write(st.session_state.processed[option][0]) to st.write(st.session_state.processed[option][0] + add)
reason: the add should be incorporated in code to show that it will work without using the expensive call