All SSML tags are malformed and do not work with Twilio

[PhilThurston]

Issue Summary

Currently all SSML tags are malformed. They are either capitalized for example the proper <emphasis> is instead generated as <Emphasis> or <say-as> is generated as <SayAs>. These generate an error code of 12200 XML Validation warning and the call fails.

Steps to Reproduce

Create a twiml with any function that is designed to inject an SSML tag.

Code Snippet

        say := &twiml.VoiceSay{}
	say.InnerElements = []twiml.Element{
		&twiml.VoiceP{Words: "This will generate the wrong SSML"}
	}

	hangup := &twiml.VoiceHangup{}

	return []twiml.Element{say, hangup}

Technical details:

• twilio-go version: All versions since Oct 2, 2022
• go version: All versions