Agora RTC Objective-C API Reference Refactor

Here is a list of all namespace members with links to the namespace documentation for each member:

### - k -

- kAdmMaxDeviceNameSize : agora::rtc
- kAdmMaxGuidSize : agora::rtc
- kDeviceIdSize : agora::rtc
- kGif : agora::rtc
- kIntervalInMillseconds : agora::rtc
- kJpeg : agora::rtc
- kMaxCharBufferLength : agora::media::base
- kMaxCodecNameLength : agora::media::base
- kPng : agora::rtc