feat(runtime-core): return onUnmounted in onMounted

[Alfred-Skyblue]

Return a function in onMounted that will be executed in onUnmounted.

RFC

onMounted(() => {
  console.log('onMounted')
  return () => {
    console.log('onUnmounted')
  }
})

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	86.5 kB (+89 B)	32.9 kB (+37 B)	29.7 kB (+2 B)
vue.global.prod.js	132 kB (+89 B)	49.6 kB (+40 B)	44.6 kB (+100 B)

Usages

Name	Size	Gzip	Brotli
createApp	48 kB (+89 B)	18.9 kB (+44 B)	17.3 kB (+87 B)
createSSRApp	51.3 kB (+89 B)	20.2 kB (+50 B)	18.4 kB (+51 B)
defineCustomElement	50.4 kB (+89 B)	19.7 kB (+40 B)	18 kB (+48 B)
overall	61.4 kB (+89 B)	23.8 kB (+40 B)	21.7 kB (+104 B)