Add documentation for bucket sort

src/sorting/bucket_sort.md

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+# Bucket Sort
+
+## Overview
+Bucket Sort is a distribution-based sorting algorithm that divides input elements into buckets and sorts each bucket individually.
+
+## Steps
+1. Create `n` empty buckets.
+2. Distribute numbers into buckets based on value ranges.
+3. Sort each bucket individually.
+4. Merge all buckets to form the final sorted list.
+
+## Time Complexity
+| Case | Time |
+|------|------|
+| Best | O(n + k) |
+| Average | O(n + k) |
+| Worst | O(n²) |
+| Space | O(n + k) |
+
+## Rust Example
+
+```rust
+pub fn bucket_sort(arr: &mut [f32]) {
+    let n = arr.len();
+    let mut buckets: Vec<Vec<f32>> = vec![Vec::new(); n];
+
+    for &value in arr.iter() {
+        let index = (value * n as f32) as usize;
+        buckets[index.min(n - 1)].push(value);
+    }
+
+    for bucket in buckets.iter_mut() {
+        bucket.sort_by(|a, b| a.partial_cmp(b).unwrap());
+    }
+
+    let mut idx = 0;
+    for bucket in buckets {
+        for value in bucket {
+            arr[idx] = value;
+            idx += 1;
+        }
+    }
+}