Add heartbeat messages #1259
Description
Current Situation
ReactPy currently uses websockets as the primary messaging method for rendering.
This can be problematic because cloud providers (such as Azure or GCP) do not keep web workers running persistently. They are run on demand and will "randomly" restart after a certain idle timeout period, which leads to a bad experience.
Proposed Actions
Add heartbeat messages to ReactPy, which will prevent cloud workers from timing out (ref)?