feat(sfc): support $shallowRef ref sugar

test-dts/refSugar.test-d.ts

@@ -1,6 +1,7 @@
 import {
   expectType,
   $ref,
+  $shallowRef,
   $computed,
   $fromRefs,
   $raw,
@@ -14,6 +15,10 @@ expectType<number>($ref(1))
 expectType<number>($ref(ref(1)))
 expectType<{ foo: number }>($ref({ foo: ref(1) }))
 
+// $shallowRef
+expectType<number>($shallowRef(1))
+expectType<{ foo: Ref<number> }>($shallowRef({ foo: ref(1) }))
+
 // $computed
 expectType<number>($computed(() => 1))
 let b = $ref(1)