fix(gtag): send the newly rendered page's title instead of the old one's

[ori-shalom]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.

Motivation

Fix #7420

Test Plan

I manually tested it with the reproduction environment on stackblitz.
I also have on my private project repo this implementation fix of the gtag plugin that I deployed and debuged using GA debug tools.
It can be clearly seen in the logs and in GA debug panel that the correct title is used now.

Test links

https://stackblitz.com/edit/github-fab3de?file=plugin%2Fclient-module.js

Deploy preview: https://deploy-preview-7424--docusaurus-2.netlify.app/

[Josh-Cena]

Please also add a brief comment explaining this, and linking to the issue.

(And fixing the syntax error, of course)

[netlify]

✅ [V2]

Name	Link
🔨 Latest commit	d1596e4
🔍 Latest deploy log	https://app.netlify.com/sites/docusaurus-2/deploys/6290dd688645ee0008c987fc
😎 Deploy Preview	https://deploy-preview-7424--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	PWA	Report
/	🟢 95	🟢 100	🟢 100	🟢 100	🟢 90	Report
/docs/installation	🟢 90	🟢 99	🟢 100	🟢 100	🟢 90	Report

[Josh-Cena]

This makes sense to me.

@slorber seems to dislike setTimeout for good reason, so I'll wait for his decision on this.

[ori-shalom]

@slorber any comment on that?

[slorber]

Related to #6732

I don't think we should ask all analytics plugin authors to use setTimeout (including ourselves)

I'd rather make it a guarantee that page metadatas/title are already updated when routeDidUpdate callback is fired

Some local tests:

The easy solution would be to move to useEffect instead of useLayoutEffect: this is nice for analytics but likely not ideal for other use-cases where we need to update the DOM synchronously

[slorber]

Waiting for an answer here: https://twitter.com/sebastienlorber/status/1530180431475265537

[slorber]

Going to merge this, as at least it fixes the GTAG plugin for the next release

But clearly we are not done yet with those lifecycles, and this setTimeout should not be necessary