Fix bip158 example formatting

src/util/bip158.rs

@@ -23,13 +23,14 @@
 //! The filter construction proposed is an alternative to Bloom filters, as used in BIP 37,
 //! that minimizes filter size by using Golomb-Rice coding for compression.
 //!
-//!  USE :
-//!   // create a block filter for a block (server side)
+//! ## Example
 //!
+//! ```ignore
 //! fn get_script_for_coin(coin: &OutPoint) -> Result<Script, BlockFilterError> {
 //!   // get utxo ...
 //! }
 //!  
+//! // create a block filter for a block (server side)
 //! let filter = BlockFilter::new_script_filter(&block, get_script_for_coin)?;
 //!
 //! // or create a filter from known raw data
@@ -41,7 +42,7 @@
 //! if filter.match_any(&block_hash, &mut query.map(|s| s.as_bytes())) {
 //!   // get this block
 //! }
-//!
+//!  ```
 //!  
 
 use std::{cmp, fmt, io};