Add rustfmt.toml file that ignore every file

[Stargateur]

This should prevent rustfmt to format any file, unfortunately the behavior of rustfmt is strange, this option is not stable (but should be soon ?), this make rustfmt pop a warning instead of an error and it format all anyway:

Warning: can't set ignore = IgnoreList { path_set: {"/"}, rustfmt_toml_path: "" }, unstable features are only available in nightly channel.

Anyway, until it's stable this at least pop a warning that should avoid #55 PR.