Optionally log timestamp (absolute or relative)

[medikoo]

It applies to writers, but environment variable and specification of settings should be defined in this repository.

Ttwo options with additional customizations should be available:

• absolute - full date & time stamp. Still we can define whether we show just time or date and time
• relative - full time since process started (alternative could be time elapsed since previous log, still it'll not work as expected in cases where logs are generated but remain not written therefore that probably shouldn't be considered)