Fix @/abc being treated as scoped module

Fixes #1851

Before this commit, @/abc was being wrongly detected as a scoped module.
This was a problem when somebody had a webpack alias `@`. (eg. @ -> ./src)

In general, scoped modules can't start with @/, I think they have to be like @/abcd.

src/core/importType.js

@@ -93,7 +93,7 @@ function typeTest(name, settings, path) {
 }
 
 export function isScopedModule(name) {
-  return name.indexOf('@') === 0
+  return name.indexOf('@') === 0 && !name.startsWith('@/')
 }
 
 export default function resolveImportType(name, context) {