Add support for Google Analitics global site tag

[thomasturrell]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/scullyio/scully/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Adds support for Google Analytics 4 properties.

Does this PR introduce a breaking change?

• Yes
• No

Other information

There are no tests in this pull request, can someone advise me what testing would be appropriate?

[SanderElias]

I'm not worried about the tests of this. But I'm worried about the backward compatibility. Is this providing the same function with an updated method, or is it providing a slightly different option?
The script looks good to me, but I don't have time to dig into the details of the GAPI on this.
Can you point me to some relevant resources?

[thomasturrell]

Please keep in mind I am no expert on Google Analytics so please check my findings and conclusions!

Google Analytics have two types of ID, the newer Google Analytics 4 properties have ID's that are prefixed "G-" and the older Universal Analytics properties have ID's that are prefixed "UA-".

Google documents the process of seeing up a Google Analytics 4 property here:
https://support.google.com/analytics/answer/9304153#zippy=%2Cweb%2Cadd-the-global-site-tag-directly-to-your-web-pages%2Cfind-your-g--id-for-any-platform-that-accepts-a-g--id

Google have a migration guide:
https://developers.google.com/analytics/devguides/migration/ua/analyticsjs-to-gtagjs

This pull request should be backwards compatible with pervious versions of Google Analytics. It adds support for D's that are prefixed "G-" sites with ID's that are prefixed "UA-" should be unaffected.

@GuzmanPI please could you have a look at this pull request, I noticed that you are the original author of this plugin.