Add flag for filtering by entry types/kinds

[jotaen]

When filtering records, it would be useful if you could filter by entry type as well, e.g. “only duration entries”, or “only open time ranges”.

The corresponding flag could be called --type (or --kind), and take a mandatory value such as:

• --type DURATION (would include both positive and negative durations)
  • --type DURATION_POSITIVE (only e.g. -45m)
  • --type DURATION_NEGATIVE (only e.g. 30m or +30m)
• --type TIME_RANGE (e.g., 8:00-9:00)
• --type OPEN_RANGE (e.g., 8:00-?)

Originated in https://github.com/jotaen/klog/discussions/285.