docs: update example usage in HeapLfuCache and correct LRU-K documentation (#78)

Modified the example usage in the `HeapLfuCache` documentation to reflect the correct module path. Updated the LRU-K documentation to improve clarity by correcting the representation of segmented LRU lists. These changes enhance the overall consistency and usability of the documentation, ensuring it aligns with Rust API guidelines.

Author: TKorr

src/policy/heap_lfu.rs

@@ -180,11 +180,9 @@
 //! ## Example Usage
 //!
 //! ```rust,ignore
-//! use crate::storage::disk::async_disk::cache::heap_lfu::HeapLfuCache;
+//! use cachekit::policy::heap_lfu::HeapLfuCache;
 //! use std::sync::Arc;
-//! use crate::storage::disk::async_disk::cache::cache_traits::{
-//!     CoreCache, MutableCache, LfuCacheTrait,
-//! };
+//! use cachekit::traits::{CoreCache, MutableCache, LfuCacheTrait};
 //!
 //! // Create cache
 //! let mut cache: HeapLfuCache<String, i32> = HeapLfuCache::new(100);

src/policy/lru_k.rs

@@ -112,7 +112,7 @@
 //! |------------------|----------------------------------------------------|
 //! | `LrukCache<K,V>` | Main cache struct with store + K value             |
 //! | `index`          | `HashMap<K, usize>` to slot indices                |
-//! | `cold`/`hot`     | Segmented LRU lists (&lt;K and >=K accesses)       |
+//! | `cold`/`hot`     | Segmented LRU lists (>K and ≥K accesses)          |
 //! | `store`          | Stores key -> `Arc<V>` ownership                   |
 //! | `k`              | Number of accesses to track (default: 2)           |
 //!