feat: add ConfigModule and FakeBackendInterceptor

Closes #34, #37

src/environments/environment.prod.ts

@@ -13,5 +13,7 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 export const environment = {
-  production: true
+  backend_url: 'http://localhost:3000',
+  backend_version: '1.0.0',
+  production: true,
 };

src/environments/environment.ts

@@ -17,7 +17,9 @@
 // `ng build --env=prod` then `environment.prod.ts` will be used instead.
 // The list of which env maps to which file can be found in `.angular-cli.json`.
 export const environment = {
-  production: false
+  backend_url: 'http://localhost:3000',
+  backend_version: '1.0.0',
+  production: false,
 };
 
 /*