Migration v1 to v2

vue-gtag@2 requires Vue 3 to be installed...and that's pretty much it!

The focus for vue-gtag@2 is compatibility. vue-gtag@2 supports Vue 3, and it provides the exact same API as vue-gtag@1, so users can reuse their existing code with Vue 3.

Changes that would reflect more the new Vue 3 workflow like composition-api and reactive data will be released with vue-gtag@3 currently available under the package vue-gtag-next