chore: update user agent string for better debugging

[philnash]

This PR standardizes the format of our User-Agent string in twilio-node and provides the ability to pass additional information from upstream packages to be included. It follows the agreed pattern of:

<core-api-lib>/<core-api-lib-version> (<os-name> <os-arch>) node/<node-version> <extensions>

Where are being added space separated following:

<library>/<library-version>

or

<tag>

In this case the Twilio class allows you to pass in userAgentExtensions as an array to specify upstream libraries who use it to add their library name and version.

This could possibly be described as a breaking change as it will update the underlying User-Agent used by the default HTTP Client and anything that relies on that will need an update. I have not marked this as breaking yet though, as I am unsure if that would be a problem and I am interested in other opinions on this.

Checklist

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

If you have questions, please file a support ticket, or create a GitHub Issue in this repository.

[thinkingserious]

I recommend marking this as a breaking change since the change could break folks.

[thinkingserious]

🎆

[philnash]

Is there anything else that needs to be done for this PR? I notice that one of the checks that is required needs to be run, how do I do that?