add a page about logging config

[tzemanovic]

Let's add a page that explains logging config. Currently, we can set NAMADA_LOG to one of: info, debug, warn, error. NAMADA_LOG_COLOR can be used to switch off colors (true/false). NAMADA_LOG_FMT can be set to full (the default), json or pretty.

Once anoma/namada#1578 is released, the NAMADA_LOG_DIR env var can be used for logging to file(s) and NAMADA_LOG_ROLLING for setting rolling logs frequency. The rolling frequency can be set to never, minutely, hourly or daily. If not set, the default is never.