Introduce envsubst for config.js, update deps (#3032)

This is the implemenation of envsubst discussed in #1756 

Documentation update will follow after merge.

tests/configs/port_variable.env

@@ -0,0 +1 @@
+MM_PORT=8090

tests/configs/port_variable.js.template

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+/* MagicMirror² Test config sample environment set port 8090
+ *
+ * By Rodrigo Ramírez Norambuena https://rodrigoramirez.com
+ * MIT Licensed.
+ */
+let config = require(process.cwd() + "/tests/configs/default.js").configFactory({
+	port: ${MM_PORT}
+});
+
+/*************** DO NOT EDIT THE LINE BELOW ***************/
+if (typeof module !== "undefined") {
+	module.exports = config;
+}

tests/e2e/template_spec.js

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+const helpers = require("./helpers/global-setup");
+
+describe("templated config with port variable", () => {
+	beforeAll(async () => {
+		await helpers.startApplication("tests/configs/port_variable.js");
+	});
+	afterAll(async () => {
+		await helpers.stopApplication();
+	});
+
+	it("should return 200", async () => {
+		const res = await helpers.fetch("http://localhost:8090");
+		expect(res.status).toBe(200);
+	});
+});