Add usage example for tszip and tsunzip

docs/cli.md

@@ -11,6 +11,13 @@ Online help is available using the `--help` option.
 
 The `tsunzip` program is an alias for `tszip -d`.
 
+To compress or decompress a single file to a different filename, simply pipe to a new file via stdout:
+
+```sh
+tszip -c myfile.trees > compressed.tsz
+tsunzip -c compressed.tsz > duplicate_myfile.trees
+```
+
 ## tszip
 
 ```{argparse}