Update introduction.mdx

Add Monite API

Author: a-akimov

integrations/introduction.mdx

@@ -359,4 +359,7 @@ For example:
   <Card title="Polar API" href="https://docs.polar.sh/api-reference">
     Pull data such as activity levels and heart rate from Polar devices.
   </Card>
-</CardGroup>
+  <Card title="Monite API" href="https://docs.monite.com/api/concepts/overview">
+    Invoice generator, bill payments, OCR, B2B payments, e-invoicing and integration with accounting systems.
+  </Card>
+</CardGroup>