Added Web RTC, Network Preferences and Support for Webhooks

WebRTC:

• Added the /telephony_credentials for Web RTC

Wireless:

• Added /mobile_operator_networks endpoint.
• Added the /ota_updates endpoint for controlling network preferences.

Webhooks:

• Added a TelnyxWebhook object and EventTypesEnum for webhook structures.
• Added examples to the examples project to showcase how to consume webhooks using the Telnyx .Net SDK.

v2.0.0: Messaging, wireless, number lookup, connections, OVPs, account endpoints added

Messaging:

• Added URL shortner payloads
• Added Messgaing Profile metrics endpoint

Wireless:

• Added SIM Cards endpoint
• Adde Mobile Network Operator endpoint

Number Lookup:

• Added Number Lookup endpoint

Connections and Outbound Voice Profiles:

• Added Connections list endpoint
• Added Outbound VOice Profiles endpoint
• Added Call Control Applications

Account:

• Added addresses endpoint

SDK Functionality:

• Pagination added (details in README)
• Made classes internal