Add new chat command: stats

[jmakhack]

Note: This is dependent on #356 so work cannot start on this issue until #356 is first completed. Work can get started before #356 is finished by just following the json schema presented in that issue.

Feature Reasoning

Given that command usage stats are now stored in a json file, it would be neat to have a chat command to read out those stat values.

Feature Description

As part of #356, basic usage stats on all chat commands are now stored as part of a json file. This feature is to implement a new chat command such that running ::hr stats (or abbreviated ::hr s) will display that usage data in the chat window.

It should be displayed similarly to: Usage stats: help - 6, prev - 8, next - 12, ....

Possible Alternatives

Any possible alternatives for how the stats are displayed in the chat window may be acceptable.

Additional Context

Please refer to CONTRIBUTING.md for info on how to setup, build, run, and test this project.