Provide default when modpack doesn't specify loader (#4930)

* fix no modpack loader, default to minecraft loader

* use v2 create then modify with v3 for environment

apps/frontend/src/components/ui/create-project-version/stages/AddFilesStage.vue

@@ -133,6 +133,8 @@ const addDetectedData = async () => {
 
 	if (projectType.value === 'resourcepack') {
 		draftVersion.value.loaders = ['minecraft']
+	} else if (projectType.value === 'modpack' && draftVersion.value.loaders?.length === 0) {
+		draftVersion.value.loaders = ['minecraft']
 	}
 }