docs(readme): add libicu package dependency

README.md

@@ -12,6 +12,8 @@ SPDX-License-Identifier: CC0-1.0
     - Python > 3.8
     - Docker > 20.10
     - Docker Compose > 1.25
+    - libicu-dev
+
 1. Create/activate virtual environment (ensure you use the correct python version!).
 
     ```sh