docs: add diagram to readme

README.md

@@ -23,3 +23,15 @@ Built with [openpassport](https://openpassport.app).
 1. On mobile app
    1. Scan QR Code shown in desktop's browser.
    2. Tap _verify_.
+
+## What is going on?
+
+![workflow diagram](./assets/dog18-diagram.svg)
+
+1. With the OpenPassport mobile app, the passport electronic data is transferred to the mobile device by near field communication.
+2. With `@openpassport/sdk`, one can generate a QR code in the web client to request the generation of a specific proof (particular set of requirements).
+3. Upon scanning this QR code, a web socket connection is opened between the mobile device and the web client.
+4. The user initiates the generation of the proof on the mobile device.
+5. The mobile device transfers this proof to the web client.
+6. The web client can now perform a verification (`snarkjs`) of this proof or transfer this proof for an authentication server to verify it.
+7. Depending on the verification result, the web client can authorize access to some restricted content.