[Draft] Feature/zap logger

[whitespire]

This PR brings in an opinionated implementation of Zap logger as a singleton module.
It was written for maximum compatibility with slog (a drop in module replacement) through creating module-level aliases for zap's field functions (so, zap.String is available as logger.String, zap.Int as logger.Int, etc).

Usage:

1. import logger package.
2. add defer logger.Sync() to main()
3. call logger.Info/Debug/Warn/Fatal just as you would with slog
4. Extra: the module assumes that the environment variable "ENV" is used to differentiate dev from production, and will create zap's Production logger if ENV=production. Most notably, prodution logger works at level Info and above and got ratelimit / sampling set up for over 100 lines / sec.

Footguns involved:

• unit tests might not play nice with a singleton like that. Might need to do logger injection down the line for that.
• not all zap's field functions are aliased yet (for example, Uint8, Stringp, Strings, etc.) Will need to add them to aliaces in current implementation.
• zap.Logger.Error() is aliased to logger.Error(), zap.Error() is unavailable. Use logger.NamedError() (alias of zap.NamedError()) for the error field type instead.

[Simon-Weij]

Why zap over just using slog? Zap seems very speed oriented, while this is a simple discord bot which probably doesn't need zap at all. IMO the standard library is more than capable for our needs