fix: export missing decorator (#104)

Author: cuebit

src/index.cjs.ts

@@ -15,6 +15,7 @@ import { HasOne } from './model/decorators/attributes/relations/HasOne'
 import { BelongsTo } from './model/decorators/attributes/relations/BelongsTo'
 import { HasMany } from './model/decorators/attributes/relations/HasMany'
 import { HasManyBy } from './model/decorators/attributes/relations/HasManyBy'
+import { MorphOne } from './model/decorators/attributes/relations/MorphOne'
 import { Attribute } from './model/attributes/Attribute'
 import { Type } from './model/attributes/types/Type'
 import { Attr as AttrAttr } from './model/attributes/types/Attr'
@@ -49,6 +50,7 @@ export default {
   BelongsTo,
   HasMany,
   HasManyBy,
+  MorphOne,
   Attribute,
   Type,
   AttrAttr,