feat: computed getter support

[harlan-zw]

(original PR)

Issue

#96, fixes #57

Solution

There are two fundamental changes to the logic:

1. Take input as is and don't wrap it in anything (ref, shallowRef, etc)
2. Resolve reactivity deeply, once, before it's rendered as a string or to DOM nodes

While this shouldn't break anything and the tests are passing, reactivity issues could potentially pop up. Will be introduced as a minor bump.

[github-actions]

Export Size

@vueuse/head

Name	Size	Diff
resolveHeadInput	199 B	+199 B (+100.00%) 🔺
stringifyAttrValue	101 B	+16 B (+18.82%) 🔺
isEqualNode	183 B	+26 B (+16.56%) 🔺
stringifyAttrName	109 B	+14 B (+14.74%) 🔺
injectHead	162 B	+16 B (+10.96%) 🔺
createHead	1.84 KB	+99 B (+5.53%) 🔺
stringifyAttrs	260 B	+12 B (+4.84%) 🔺
setAttrs	219 B	+10 B (+4.78%) 🔺
tagDedupeKey	276 B	+12 B (+4.55%) 🔺
sortTags	185 B	+8 B (+4.52%) 🔺
createElement	220 B	+8 B (+3.77%) 🔺
tagToString	424 B	+12 B (+2.91%) 🔺
Head	531 B	+11 B (+2.12%) 🔺
updateElements	769 B	+11 B (+1.45%) 🔺
renderHeadToString	741 B	-9 B (-1.20%) 🔽

Unchanged

@vueuse/head

Name	Size	Diff
useHead	244 B	-