Enable setting a custom Logger

[rahearn]

Metanorma PR checklist

• [ ] Breaking changes (list related PRs)
• [ ] Documentation update required (create task for this)
• [ ] External dependency introduced (documentation update need)
• [ ] Gem with native library introduced

Allows setting a new logger (such as Oscal::ParsingLogger.logger = Rails.logger) instead of dumping everything to stdout at all times.

[ronaldtse]

Thank you @rahearn !