Mention that formatting can be skipped per line using [cairofmt::skip]

[0xNeshi]

Problem

Nowhere is it mentioned that specific lines can be marked with #[cairofmt::skip] to skip formatting them when running scarb fmt. This is a very useful feature that should be included in the docs (I had to dig through the Cairo language repo to find (the issue](starkware-libs/cairo#4159)).

Proposed Solution

Update "Formatting" page to include a mention of this feature:
https://docs.swmansion.com/scarb/docs/guides/formatting.html

Notes

This is a very useful thing to know, especially when needing to custom format arrays for clarity, e.g. to represent some table like:

    #[cairofmt::skip]
    let table = array![
        "oxo",
        "xox",
        "oxo",
    ];

This feature was implemented with starkware-libs/cairo#4159