docs(readme): secret example

README.md

@@ -112,6 +112,14 @@ Pseudonomyzation requires an RDF file, index and config as input:
 tripsu pseudo --index index.nt --config rules.yaml input.nt > output.nt
 ```
 
+>[!NOTE]
+> By default, pseudonymization uses a random seed. To make the process deterministic, you may provide a secret.
+
+```shell
+echo "The quick brown fox jumps over the lazy dog" > secret.txt
+tripsu pseudo -s secret.txt -x index.nt -c rules.yaml input.nt > output.nt
+```
+
 > [!TIP]
 > For each subcommand, you can use `--help` to see all options.