Update README.md with rayon and multithreading section

README.md

@@ -99,14 +99,15 @@ let mappings: Result<Vec<Mapping>> = aligner.map_file("query.fa", false, false);
 ## Multithreading
 Multithreading is supported, for implementation example see [fakeminimap2](https://github.com/jguhlin/minimap2-rs/blob/main/fakeminimap2/src/main.rs). Minimap2 also supports threading itself, and will use a minimum of 3 cores for building the index. Multithreading for mapping is left to the end-user.
 
+Adjust the number of threads used to build the index:
 ```rust
 let mut aligner = Aligner::builder()
     .map_ont()
     .with_index_threads(8);
 ```
 
 ### Experimental Rayon support
-This _appears_ to work.
+This _appears_ to work. See [fakeminimap2](https://github.com/jguhlin/minimap2-rs/tree/main/fakeminimap2) for full implementation.
 
 ```rust
 use rayon::prelude::*;
@@ -116,6 +117,9 @@ let results = sequences.par_iter().map(|seq| {
 }).collect::<Vec<_>>();
 ```
 
+### Arc cloning the Aligner
+Also works. Otherwise directly cloning the aligner will Arc clone the internal index.
+
 ## Features
 The following crate features are available:
 * map-file - Enables the ability to map a file directly to a reference. Enabled by deafult