chore: move express.d.ts

Author: jonathannorris

Diff for: src/express.d.ts

@@ -0,0 +1,7 @@
+import { DevCycleUser } from '@devcycle/nodejs-server-sdk';
+
+declare module 'express-serve-static-core' {
+  interface Request {
+    user: DevCycleUser;
+  }
+}