classic chat interface

[pavlozt]

Could you change the example to a classic chat interface in example program? Message history at the top, buttons at the bottom, the new message is empty and is added at the bottom on the first submit.

I understand that the example is made to magically solve a difficult streamlit problems: the inability to display not yet existing variables. But since you set the tone for many novice programmers, could you remake the example?

Another confirmation that people need it is here - #17