feat: add multiRoot marker for template-only vapor component (#385)

Author: edison1105

src/transform.ts

@@ -383,7 +383,8 @@ async function doCompileTemplate(
       expressionPlugins,
     },
   })
-  let { code, errors, map } = res
+  // @ts-expect-error multiRoot in 3.6
+  let { code, errors, map, multiRoot } = res
   if (errors.length) {
     return { code, map, errors }
   }
@@ -396,6 +397,10 @@ async function doCompileTemplate(
       `$1 ${fnName}`,
     )}` + `\n${COMP_IDENTIFIER}.${fnName} = ${fnName}`
 
+  if(descriptor.vapor && !ssr) {
+    code += `\n${COMP_IDENTIFIER}.__multiRoot = ${multiRoot}`
+  }
+
   if (isTS) {
     code = await transformTS(code, isJSX)
   }