Adds heartbeat to prevent Websocket closing

[RobertLowe]

This change ensures Firefox (and others?) don't close connection when detected as idle with a CloseEvent of 1006. This is an opinionated change due to when using ws.onclose on the client. This is entirely committed for note and posterity.

Cheers

[jenkinskurento]

Hi there. Thanks for your PR.

I'm waiting for a Kurento member to verify that this patch is reasonable to test. If it is, they should reply with check out please on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

[jenkinskurento]

There were no errors, go have a cup of coffee...

[jenkinskurento]

There were no errors, go have a cup of coffee...