feat: add refetch_frequency parameter to settings

[gabriel-ss]

⚡ Summary

First of all, thanks everyone for the great tool!

The remote feature of lefthook allows us at the place where I work to easily share configuration across our hundreds of repositories. Usually, our devs have some dozens of repositories cloned on their machines and work actively in one or two at a time. To ensure that they will have a reasonably recent config when going back to a repo after some time, we configure our remotes with refetch: true, but this has the side effect that every time they run lefthook on a currently active repository, either by commiting something or by hand to manually check the output of the QA tools, they trigger a fetch.

To make the experience smother, this PR introduces a new parameter refetch_frequency that allows a more fine grained control over the remote refetching by allowing the definition of time periods instead of just a boolean flag. This is a working implementation already, but it defers some decisions that could be made to maybe improve the usability. I didn't want to touch the following points without consulting the core team before, but:

• I think that this parameter superseds the current refetch, so maybe it could be marked deprecated;
• I used ParseDuration from go's stdlib in the current implementation, but a more user-friendly format could be used at the cost of a new dependency.

I also apologize in advance for any oddities in the code, I'm not a go programmer, but I can make changes that you see fit to make the PR more fitting.

☑️ Checklist

• Check locally
• Add tests
• Add documentation

[mrexox]

Wow! Thank you for providing this PR! I will review it this week and will release if everything is good 👍

[mrexox]

Check out 1.8.2 version!