feat: Update README and add requirements.txt for rich library installation instructions

docker-manager/README.md

@@ -18,10 +18,11 @@ A Python command-line application to manage Docker containers defined in subdire
 
 - Python 3
 - Docker and Docker Compose (plugin) installed.
-- The `rich` Python library:
+- Python dependencies:
   ```bash
-  pip install rich
+  pip install -r ~/shell/docker-manager/requirements.txt
   ```
+  *Or manually:* `pip install rich`
 - A `~/docker/` directory containing subdirectories for each of your projects.
 - Each project subdirectory must contain a `docker-compose.yml`, `docker-compose.yaml`, `compose.yml`, or `compose.yaml` file.