docs(integration-examples): add "config.ts" file for jest example

fixes #520
fixes #519

Author: hasezoey

docs/guides/integration-examples.md

@@ -11,6 +11,18 @@ This Guide will show how `mongodb-memory-server` can be used with different fram
 
 For useage with `jest` it is recommended to use the [`globalSetup`](https://jestjs.io/docs/en/configuration#globalsetup-string) and [`globalTeardown`](https://jestjs.io/docs/en/configuration#globalteardown-string) options
 
+`config.ts`:
+
+```ts
+// this file could be anything (like a json directly imported)
+
+export = {
+  Memory: true,
+  IP: '127.0.0.1',
+  Port: '27017',
+}
+```
+
 `jest.config.json`:
 
 ```ts