Apply rustfmt to the codebase

[Delapouite]

Hello.

While I was skimming through the codebase through github.com, I was surprised to stumble upon very weirdly indented code which was very hard to follow :

Here's an example take from item.rs :

Indeed, after git cloning the repo on my local station, it turns out that the source code uses a mixed bag for spaces and tabs, so the problem remain in my text-editor.

I reckon it could be worthwhile to perform some cleanup with rustfmt across all rust files in order to alleviate the problem.

Thanks.

[Shizcow]

I've added make fmt which does the pre-requisite setup and then calls rustfmt. Unfortunately due to how the build system is set up, adding a github action to do this is not easily possible.