Warning js vue component

[miaulightouch]

if there's at least one js vue component referenced, it would cause error when building.

maybe it should warn user check the type, or just ask user change "allowJs" option to true in tsconfig.json?

[qmhc]

This is the behavior of typescript that will only cause the declaration files generation to fail.

But it is not a good experience really, some optimizations will be done later.