Update theme with new Google Analytics code

[mattstratton]

WARN  deprecated: .Site.GoogleAnalytics was deprecated in Hugo v0.120.0 and will be removed in a future release. Use .Site.Config.Services.GoogleAnalytics.ID instead.

[toshywoshy]

The documentation states the deprecation, however does not provide a "good practice" solution.
I would say to create an own version of GA javascript code and use the same veriables to avoid any updates, this is similar to what we use with Matomo.