build: add type module to package.json (#1382)

Author: CaerusKaru

projects/libs/flex-layout/package.json

@@ -34,5 +34,6 @@
     "@angular/common": "0.0.0-NG",
     "@angular/platform-browser": "0.0.0-NG",
     "rxjs": "^6.5.3 || ^7.4.0"
-  }
+  },
+  "type": "module"
 }