add module for formatters and linters

[nrdxp]

Since most of our projects use treefmt, it seems like a bit of an oversight that we don't include it in the devshell, at least optionally.

[blaggacao]

This was actually removed on purpose to enable transition to nixago, see: IntersectMBO/cardano-world#36

The reason is that the two versions of e.g. treefmt might easily conflict.

It was just the latest commit which removed it for that purpose: 125b866

Would you still want to have a formatters capsule or would transition to nixago actually be beneficial and receive an additional impulse by the lack of a formatters capsule? (And via the context of this PR)

[nrdxp]

Well just in case this wasn't accepted, I went ahead and solved this another way for now:
https://github.com/input-output-hk/mamba-world/pull/839

[blaggacao]

I'm still not sure on your preferences, here: is it for nixago or to get this PR merged as a bridge?

I'm fine with both, if you have a strong opinion.

[nrdxp]

I guess I'm just not seeing how the two conflict exactly...

[blaggacao]

Nixago should be the blessed path forward because its generalized capabilities.

So the question is if you would mind to switch right away or if you'd prefer to provide this temporary "work-around".