Add examples for min and max functions (#9062)

# Which issue does this PR close?

- Closes #9055.

# What changes are included in this PR?

Changes to docstrings for `min` and `max` functions.

# Are these changes tested?

Yes

# Are there any user-facing changes?

Yes. These doc pages will be updated:
https://docs.rs/arrow/latest/arrow/compute/fn.min.html
https://docs.rs/arrow/latest/arrow/compute/fn.max.html

Author: EduardAkhmetshin

arrow-arith/src/aggregate.rs

@@ -809,6 +809,15 @@ where
 
 /// Returns the minimum value in the array, according to the natural order.
 /// For floating point arrays any NaN values are considered to be greater than any other non-null value
+///
+/// # Example
+/// ```rust
+/// # use arrow_array::Int32Array;
+/// # use arrow_arith::aggregate::min;
+/// let array = Int32Array::from(vec![8, 2, 4]);
+/// let result = min(&array);
+/// assert_eq!(result, Some(2));
+/// ```
 pub fn min<T: ArrowNumericType>(array: &PrimitiveArray<T>) -> Option<T::Native>
 where
     T::Native: PartialOrd,
@@ -818,6 +827,15 @@ where
 
 /// Returns the maximum value in the array, according to the natural order.
 /// For floating point arrays any NaN values are considered to be greater than any other non-null value
+///
+/// # Example
+/// ```rust
+/// # use arrow_array::Int32Array;
+/// # use arrow_arith::aggregate::max;
+/// let array = Int32Array::from(vec![4, 8, 2]);
+/// let result = max(&array);
+/// assert_eq!(result, Some(8));
+/// ```
 pub fn max<T: ArrowNumericType>(array: &PrimitiveArray<T>) -> Option<T::Native>
 where
     T::Native: PartialOrd,