feat: add phase 6 js_library and ts_library bootstrap

tests/library_test/app.test.ts

@@ -0,0 +1,6 @@
+import { expect, test } from "bun:test";
+import { greeting } from "./helper";
+
+test("uses helper from ts_library dep", () => {
+  expect(greeting("test")).toBe("hello-test");
+});