docs(hmr): improve handleHotUpdate and add further reading

[bluwy]

Description

close #15215

Also added a link to https://bjornlu.com/blog/hot-module-replacement-is-easy 🙈

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[bluwy]

Ideally I think, we shouldn't need to have user invalidate this way. This line

vite/packages/vite/src/node/server/index.ts

Lines 723 to 724 in e4ea7dd

	// invalidate module graph cache on file change
	moduleGraph.onFileChange(file)

Should already cover the invalidation, but this code here is to also invalidate for HMR (forth param). The param is used for

vite/packages/vite/src/node/server/moduleGraph.ts

Lines 186 to 192 in e4ea7dd

	if (isHmr) {
	mod.lastHMRTimestamp = timestamp
	} else {
	// Save the timestamp for this invalidation, so we can avoid caching the result of possible already started
	// processing being done for this module
	mod.lastInvalidationTimestamp = timestamp
	}

But I was thinking of combining the two timestamps in the future. And then we can remove the HMR param.