cli.plugins: include version number in `sopel-plugins show`

[dgw]

Description

There are definitely more improvements I'd like to make in the sopel-plugins CLI (e.g. #2459), but this one is simple enough to ship with a patch release.

Several times, I've wished that it was possible to see which version of a plugin Sopel sees without starting the bot to use the .version pluginname command on IRC.

Checklist

• [x] I have read CONTRIBUTING.md
• [x] I can and do license this contribution under the EFLv2
• [x] No issues are reported by make qa (runs make lint and make test)
• [x] I have tested the functionality of the things this change touches