feat(lsp): code action for unused variable

[0xLucqs]

This change is 

[orizi]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @LucasLvy and @mkaput)

---

crates/cairo-lang-diagnostics/src/error_code.rs line 76 at r1 (raw file):

pub mod codes {
    /// Unused variable
    pub const UNUSED_VARIABLE: &str = "E0001";

Suggestion:

pub mod codes {
    /// Unused variable.
    pub const UNUSED_VARIABLE: &str = "E0001";

[0xLucqs]

Reviewable status: 3 of 4 files reviewed, 1 unresolved discussion (waiting on @mkaput and @orizi)

---

crates/cairo-lang-diagnostics/src/error_code.rs line 76 at r1 (raw file):

pub mod codes {
    /// Unused variable
    pub const UNUSED_VARIABLE: &str = "E0001";

Done.

[orizi]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mkaput)