fix: SSML tag name capitalised issue

[abhishek-eltropy]

Fixes

https://github.com/twilio/twilio-go/issues/207

Currently, in twilio go sdk, Ssml tags are capitalized causing error in TwiML apps.

Warning [12200](https://www.twilio.com/docs/api/errors/12200)
Message: XML Validation warning

As per twilio docs, updated the tag name for the supported TwiML tags.

Also, verified the same with the corresponding implementation in java sdk. Ref: https://github.com/twilio/twilio-java/tree/main/src/main/java/com/twilio/twiml/voice Ref Files:

• SsmlBreak.java
• SsmlEmphasis.java
• SsmlLang.java
• SsmlP.java
• SsmlPhoneme.java
• SsmlProsody.java
• SsmlS.java
• SsmlSayAs.java
• SsmlSub.java
• SsmlW.java

Checklist

• [x] I acknowledge that all my contributions will be made under the project's license
• [x] I have made a material change to the repo (functionality, testing, spelling, grammar)
• [x] I have read the Contribution Guidelines and my PR follows them
• [x] I have titled the PR appropriately
• [x] I have updated my branch with the main branch
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have added the necessary documentation about the functionality in the appropriate .md file
• [x] I have added inline documentation to the code I modified

[AsabuHere]

These files are auto generated in every release(if there are new changes). This fix need another PR to yoyodyne repo which generates these files. Otherwise these changes will be overwritten in the next release. The yoyodyne changes needs a detailed analysis and more work which may take some more time. We will keep the issue thread posted about the progress

[abhishek-eltropy]

@AsabuHere Ok. Thanks for the review and the explanation.

Since yoyodyne repo is internal to Twilio, I don't have access to it. I will close this PR then. Hope, Twilio team will fix this sooner.

[AsabuHere]

Sure, We are working on this issue in the current sprint. Can you share some code snippets with which this issue can be reproduced? Thanks in Advance

[abhishek-eltropy]

ssmlBreak := twiml.VoiceBreak{
    Time: "1s",
}

chooseQueueSay := twiml.VoiceSay{
    Message:       "Please select one of the following",
    Voice:         "Polly.Joanna-Neural",
    InnerElements: []twiml.Element{ssmlBreak},
}

say1 := twiml.VoiceS{
    Words: "Press 1 for Loans.",
}
say2 := twiml.VoiceS{
    Words: "Pres 2 for queries.",
}

chooseQueueSay.InnerElements = append(chooseQueueSay.InnerElements, say1, ssmlBreak, say2)

voiceResponse, err := twiml.Voice([]twiml.Element{chooseQueueSay})
if err != nil {
    fmt.Println("Error: ", err)
    return
}

fmt.Println("voiceResponse", voiceResponse)

[abhishek-eltropy]

Above snippet will generate following xml:

`<?xml version="1.0" encoding="UTF-8"?>

Please select one of the following Press 1 for Loans. Pres 2 for queries. ` However, it should be - ` Please select one of the following Press 1 for Loans. Pres 2 for queries. ` Please note that break and s tags were capitalized in the generated xml.