Fix output files rendering error (missing line)

docs/output.md

@@ -80,6 +80,7 @@ The `--save_unaligned` parameter enables to obtain FastQ files containing unmapp
 
 <details markdown="1">
     <summary>Output files</summary>
+
 - `<ALIGNER>/library/unmapped/`
   - `*.fastq.gz`: If `--save_unaligned` is specified, FastQ files containing unmapped reads will be placed in this directory.