feat($plugin-google-analytics): ga4(fix #2713)

[zhouLion]

Summary

What kind of change does this PR introduce? (check at least one)

• [ ] Bugfix
• [x] Feature
• [ ] Code style update
• [ ] Refactor
• [ ] Docs
• [ ] Build-related changes
• [ ] Other, please describe:

If changing the UI of default theme, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)

You have tested in the following browsers: (Providing a detailed version will be better.)

• [x] Chrome
• [ ] Firefox
• [x] Safari
• [ ] Edge
• [ ] IE

If adding a new feature, the PR's description includes:

• [x] A convincing reason for adding this feature
• [ ] Related documents have been updated
• [ ] Related tests have been updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information: Google Analytics 4 is a new kind of property and the plugin-google-analytics doesn't support it.

This PR implements the plugin-google-analytics's support for GA4 by adding the gm(short for 'googletagmanager') property in the plugin options. I'll commit the related documents while this PR is accepted.