add missing simple test file for generating a qr code

tests/online/test_0_qr.py

@@ -0,0 +1,8 @@
+
+
+from deploy_chatmail.genqr import gen_qr_png_data
+
+
+def test_gen_qr_png_data(maildomain):
+    data = gen_qr_png_data(maildomain)
+    assert data