Add spec for verification by QR codes.

data/event-schemas/schema/m.key.verification.start$m.reciprocate.v1.yaml

@@ -0,0 +1,44 @@
+---
+allOf:
+  - $ref: core-event-schema/event.yaml
+
+description: |-
+  Begins a key verification process using the `m.reciprocate.v1` method, after
+  scanning a QR code.
+properties:
+  content:
+    properties:
+      from_device:
+        type: string
+        description: |-
+          The device ID which is initiating the process.
+      transaction_id:
+        type: string
+        description: |-
+          Required when sent as a to-device message. An opaque identifier for
+          the verification process. Must be unique with respect to the devices
+          involved. Must be the same as the `transaction_id` given in the
+          `m.key.verification.request` if this process is originating from a
+          request.
+      method:
+        type: string
+        enum: ["m.reciprocate.v1"]
+        description: |-
+          The verification method to use.
+      secret:
+        type: string
+        description: |-
+          The shared secret from the QR code, encoded using unpadded base64.
+      m.relates_to:
+        allOf:
+          - $ref: m.key.verification.m.relates_to.yaml
+    required:
+      - from_device
+      - method
+      - secret
+    type: object
+  type:
+    enum:
+      - m.key.verification.start
+    type: string
+type: object