El De-dog-lo

p.s. was trying to tackle this in #78 if you want to take the torch on that

> I'm not so sure we need to update the docs. We have the `quickstart.md` page, where I think this information is better off existing. Maybe in the `development.md` we...

After these, I think it will look pretty good

~~Upgraded this, but need to figure out why crons aren't triggering~~ --- Edit: figured out it was due to an internal failure [7a93ab3](https://github.com/ApeWorX/silverback/pull/56/commits/7a93ab301c14ae9d308eed45554382f7b529adcb), which weren't getting displayed properly [b77e718](https://github.com/ApeWorX/silverback/pull/56/commits/b77e7183ea5fca86bf5754a15f55ded7d1b0bd2d)

p.s. this website had some good test cases: https://crontab.guru/

closed in favor of #230

Have to debug why shutdown tasks are not running with this

Gonna just re-open this one under a new PR

> This all sounds good and seems pretty clear. > > Only thing I wonder is if we should either error or otherwise handle other return types for backwards compatibility...

Tested this and got pretty good results! Add some test cases, and this is probably close to merge