Channels enum

Defines values for ChannelIds for Channels. Possible values include: 'alexa', 'console', 'cortana', 'directline', 'directlinespeech', 'email', 'emulator', 'facebook', 'groupme', 'kik', 'line', 'msteams', 'onmichannel', 'outlook', 'skype', 'skypeforbusiness', 'slack', 'sms', 'telegram', 'test', 'twilio-sms', 'webchat'