Doc - Describe `expect_revert` using Rustdoc comments (three slashes: ///)

[Eikix]

In an effort of having fully documented code, we need the way we expect reverted calls to be documented.

In src/hints/expect_revert, please proceed to comment above the pub fn expect_revert declaration in an equivalent way as pub fn compile is documented.

[bacharif]

I take

[tdelabro]

closed by #95