Improve dice rolling for discourse-narrative-bot

[maiki]

@Ed_S

It might prefer odd numbers, or prefer not to roll doubles, or anything really.

You can check the randomizing code at https://github.com/discourse/discourse-ai/blob/main/lib/ai_bot/tools/random_picker.rb. For instance, dice rolls appear to be determined by:

lib/ai_bot/tools/random_picker.rb