refactor directory structure and modularize a few common functions

test/index.spec.js

@@ -0,0 +1,15 @@
+/* eslint-env node, mocha */
+import { execFile } from "child_process";
+import assert from "assert";
+import hugo from "../index.js";
+
+it("Hugo exists and runs?", async function () {
+  this.timeout(30000); // increase timeout to an excessive 30 seconds for CI
+
+  assert(execFile(hugo, ["env"], function (error, stdout) {
+    if (error) {
+      throw error;
+    }
+    console.log(stdout);
+  }));
+});