Update .gitignore and protect environment files

.gitignore

@@ -5,6 +5,10 @@
 /tmp
 /out-tsc
 
+#environments
+/src/environments/environment.ts
+/src/environments/environment.prod.ts
+
 # dependencies
 /node_modules
 

src/environments/environment_demo.ts

@@ -0,0 +1,23 @@
+// This file can be replaced during build by using the `fileReplacements` array.
+// `ng build ---prod` replaces `environment.ts` with `environment.prod.ts`.
+// The list of file replacements can be found in `angular.json`.
+
+export const environment = {
+  production: false,
+  firebase: {
+    apiKey: "",
+    authDomain: "",
+    databaseURL: "",
+    projectId: "",
+    storageBucket: "",
+    messagingSenderId: ""
+  }
+};
+
+/*
+ * In development mode, to ignore zone related error stack frames such as
+ * `zone.run`, `zoneDelegate.invokeTask` for easier debugging, you can
+ * import the following file, but please comment it out in production mode
+ * because it will have performance impact when throw error
+ */
+// import 'zone.js/dist/zone-error';  // Included with Angular CLI.