Expand flags, sort output, improve formatting

• The flags input now supports a JSON object for when you want to pass flags to specific checks, especially when running more than one at a time.
• The output from failed checks is sorted, now, so that everything is in order by file path and line number, making it easier to find and fix problems.
• The output formatting has been improved somewhat, mostly in the action logs. Comments shouldn't be impacted by the adjustments, but logs should be easier to navigate and use.

Full Changelog: v1.3.0...v1.3.1