use $ref() sugar instead of ref()

[mariusa]

Hi,

I think $ref() is simpler than ref() (no need for .value boilerplate)
eg in https://github.com/antfu/vitesse/blob/main/src/stores/user.ts

 const savedName = $ref('')
 const previousNames = $ref(new Set<string>())

  const usedNames = computed(() => Array.from(previousNames))
  const otherNames = computed(() => usedNames.filter(name => name !== savedName))
...

`$ref` can be enabled in vite config:
```js
 plugins: [
        vue({
            include: [/\.vue$/, /\.md$/],
            script: {
                refSugar: true,
            },
        }),

[antfu]

Yeah, probably when it's stable