core: Fix panic on division by integer 0 (#180)

Division by `0isize` now behaves the same as division by `0f64`.
Both produce `+inf.0`.

```scheme
(= (/ 1 0) (/ 1 0.0)) ; => #true
```

crates/steel-core/src/primitives/numbers.rs

@@ -214,6 +214,7 @@ pub fn divide_primitive(args: &[SteelVal]) -> Result<SteelVal> {
     let recip = |x: &SteelVal| -> Result<SteelVal> {
         match x {
             SteelVal::IntV(n) => match i32::try_from(*n) {
+                Ok(0) => Ok(SteelVal::NumV(f64::INFINITY)),
                 Ok(n) => Rational32::new(1, n).into_steelval(),
                 Err(_) => BigRational::new(BigInt::from(1), BigInt::from(*n)).into_steelval(),
             },
@@ -1086,6 +1087,14 @@ mod num_op_tests {
         );
     }
 
+    #[test]
+    fn dvision_by_integer_zero_returns_positive_infinity() {
+        assert_eq!(
+            divide_primitive(&[IntV(1), IntV(0)]).unwrap().to_string(),
+            NumV(f64::INFINITY).to_string()
+        )
+    }
+
     #[test]
     fn division_on_single_integer_returns_reciprocal_rational() {
         assert_eq!(