Explicitly leak to global scope instead of implicitly so strict mode and preprocessing can be used

Attached patch moves everything within the closure, declares window as a passed variable and then attached the variables to the window object that way for both gtag.js and gtm.js. It also adds "use strict" at the top of both and removes the exclusion from preprocessing.
If there is a different reason they are excluded from preprocessing, let me know and I'll remove that part from the patch.

Fix typo.

It suddenly dawned on me that I had done a "git add ." after putting the first patch in the same folder, adding the entire first patch to the second...

Remember kids, don't write patches until you've had your coffee, or at least manually review the contents of what you're uploading.

Attached patch should be correct, also moves the "use strict" inside the closure/IIFE/whatever we're calling it nowadays.

@seutje thanks, I think this is a good improvement, but could you please put the final changes to review into a MR here?

Added MR for quick review.