Log Message:
conftest: Update to 0.31.0

Potentially breaking changes:
 - JUnit output now includes OPA namespace in test name for better grouping
 - Output for parse command only emits valid JSON

New features:
 - Support for JSONC files. Thank you @greggroth!

Other Improvements:
 - Bump OPA to v0.39.0
 - Bump Golang to v1.18.1
 - Builds now include ppc64le architecture. Thank you @seth-priya!