[Feature request] Add plugin for Google Analytics 4

[meteorlxy]

Feature request

Description

Google Analytics 4 is a breaking version, and we'd better support it via different plugin than Google Analytics 3.

Related issue: vuejs/vuepress#2713

Proposed Solution

• Rename current @vuepress/plugin-google-analytics to @vuepress/plugin-google-analytics-3
• Support Google Analytics 4 in the new @vuepress/plugin-google-analytics

Alternative:

• Replace @vuepress/plugin-google-analytics with Google Analytics 4, and drop Google Analytics 3 support