Add CI config for the extension

10 jobs for topic/default/add-ci in 2 minutes (queued for 1 second)
Name Stage Failure
tests-4.5 Test
+  (use 'hg help' for the full list of commands or 'hg -v' for details)
+ [255]

ERROR: test-graphviz.t output changed
Failed test-graphviz.t: output changed
# Ran 1 tests, 0 skipped, 1 failed.
python hash seed: 3661739480
ERROR: Job failed: exit code 1