Simplify build process by auto-installing npm packages and simplify the contributor guide (#1799)

* Clarify some of the contributing building instructions

* Bump wasm-bindgen version

* Simplify build process and improve docs

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

frontend/package-installer.js

@@ -0,0 +1,34 @@
+// This script automatically installs the npm packages listed in package-lock.json and runs before `npm start`.
+// It skips the installation if this has already run and neither package.json nor package-lock.json has been modified since.
+
+import { execSync } from "child_process";
+import { existsSync, statSync, writeFileSync } from "fs";
+
+const INSTALL_TIMESTAMP_FILE = "node_modules/.install-timestamp";
+
+// Checks if the install is needed by comparing modification times
+const isInstallNeeded = () => {
+	if (!existsSync(INSTALL_TIMESTAMP_FILE)) return true;
+
+	const timestamp = statSync(INSTALL_TIMESTAMP_FILE).mtime;
+	return ["package.json", "package-lock.json"].some((file) => {
+		return existsSync(file) && statSync(file).mtime > timestamp;
+	});
+};
+
+// Run `npm ci` if needed and update the install timestamp
+if (isInstallNeeded()) {
+	try {
+		// Check if packages are up to date, doing so quickly by using `npm ci`, preferring local cached packages, and skipping the package audit and other checks
+		execSync("npm ci --prefer-offline --no-audit --no-fund", { stdio: "inherit" });
+		// Touch the install timestamp file
+		writeFileSync(INSTALL_TIMESTAMP_FILE, "");
+	} catch (error) {
+		// eslint-disable-next-line no-console
+		console.error("Failed to install npm packages. Please run `npm install` from the `/frontend` directory.");
+		process.exit(1);
+	}
+} else {
+	// eslint-disable-next-line no-console
+	console.log("All npm packages are up-to-date.");
+}