feat: add `mentions` command to show text for each label

[mikix]

This allows you to see the actual text used for each label, broken out by annotator and chart.

I also changed the order of the labels output to put the Label column before the Chart Count column, since for my brain at least, the Label is more "upstream" of the Chart Count, which is derived information from the label.

Similarly, the new mentions command puts Mentions before Label, since the Label is derived information from the mention.

Fixes #39

Checklist

• [x] Consider if documentation (like in docs/) needs to be updated
• [x] Consider if tests should be added