contrib: add generate_payreqpb2.sh script

contrib/generate_payreqpb2.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# Generates the file paymentrequest_pb2.py
+
+CONTRIB="$(dirname "$(readlink -e "$0")")"
+EL="$CONTRIB"/../electrum
+
+if ! which protoc > /dev/null 2>&1; then
+    echo "Please install 'protoc'"
+    echo "If you're on Debian, try 'sudo apt install protobuf-compiler'?"
+    exit 1
+fi
+
+protoc --proto_path="$EL" --python_out="$EL" "$EL"/paymentrequest.proto