Add dialout support for the Twilio bot in the phone example

[chadbailey59]

#998 added dial-out support for the Daily transport to the phone chatbot example. We need to add a dial-out example for Twilio as well, and clean up the Twilio dial-in README.

[vr000m]

Here is a guide to do it. Most of the configuration is on Twilio. The bot code only swaps out the phoneNumber for a sipUri

https://www.notion.so/dailyco/PUBLIC-Doc-Integration-Twilio-PSTN-Daily-s-SIP-Dialout-1cfdaed630f5458d9d4fc0e3f29ec559

for example, on L85 you can do a check for twilio vs daily.

"sipUri":"sip:{phoneNumber}@daily-twilio-integration.sip.twilio.com;transport=tls"