Add missing docs

Author: DLBPointon

README.md

@@ -83,7 +83,8 @@ Currently, the pipeline uses the following flags:
 - `--run_ultra`
   - A string argument to run the pipeline in ultra resolution mode, i.e., generate ultra resolution maps. Options are: `yes`, `force`, `no`. Default is `yes`, this runs ultra resolution maps is the genome file is > 4.Gb.
 
-- ## `--snapshot_order`
+- `--snapshot_order`
+  - A path to a `genome`, `sizes` or `fai` file containing the scaffolds in the order required for the output snapshot png file.
 
 Now, you can run the pipeline using: