Support intervals/durations

[JuniorJPDJ]

Hi! Good work guys, your lib is amazing! I'm interested in parsing intervals/durations as a duration, not a date. What do you think about creating separate function with this? There's lack of parsers like this as far as I see.

I'd like to be able to parse "1d2h3m" like dates but also in another format, which seems to work at least good with this lib, but doing (datetime.datetime.now() - dateparser.parse("30min")) doesn't seem right and also allows doing very weird and confusing things with input.