feat: implement Display trait for i257 (#327)

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## Pull Request type

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- [ ] Bugfix
- [x] Feature
- [ ] Code style update (formatting, renaming)
- [ ] Refactoring (no functional changes, no API changes)
- [ ] Build-related changes
- [ ] Documentation content changes
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## What is the current behavior?

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Issue Number: N/A

## What is the new behavior?

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- Implemented Display trait for `i257`

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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packages/math/src/i257.cairo

@@ -1,3 +1,4 @@
+use core::fmt::{Display, Formatter, Error};
 use core::num::traits::Zero;
 use core::ops::{AddAssign, SubAssign, MulAssign, DivAssign, RemAssign};
 
@@ -353,3 +354,14 @@ impl FeltIntoI257 of Into<felt252, i257> {
         i257 { abs: self.into(), is_negative: false }
     }
 }
+
+// Implements the Display trait for i257.
+pub impl DisplayI257Impl of Display<i257> {
+    fn fmt(self: @i257, ref f: Formatter) -> Result<(), Error> {
+        if *self.is_negative {
+            write!(f, "-")?;
+        }
+        self.abs.fmt(ref f)
+    }
+}
+