Allow environment variables to control loglevels

[Yamboy1]

A very useful feature I think would be to allow someone to set the log level through an environment variable, even if it's just for debug. So you can do something like

$ DEBUG=1 deno script.ts

and it will print debug logs, overriding the settings in createLogger.

It's currently possible to do this by adding a ternary condition when instantiating the logger, however I feel this would be better off in the module itself

const logger = createLogger({
  minimumLevel: Deno.env.get("DEBUG") ? LogLevel.DEBUG : LogLevel.INFO
  outputFormat: textFormat
})

It would need to be toggleable through a setting (default to true ofc), maybe something like this:

const logger = createLogger({
  debugEnv: true, // This will allow you to use the DEBUG env variable
  minimumLevel: LogLevel.INFO
  outputFormat: textFormat
})