Remove Firebase hosting, back to Express

modules/utils/secret.js

@@ -0,0 +1,8 @@
+import invariant from 'invariant';
+
+const secretKey = process.env.SECRET_KEY;
+
+invariant(secretKey, 'Missing $SECRET_KEY environment variable');
+
+export const privateKey = secretKey.private;
+export const publicKey = secretKey.public;