feat: update Docker usage instructions to create a volume for persistent storage

README.md

···
 Or with docker:
 
 ```bash
-docker run --rm -it -v $(pwd):/app tsiry/vmlinux-builder:latest 6.17.7
+docker volume create linux-build
+docker run --rm -it -v linux-build:/app tsiry/vmlinux-builder:latest 6.17.7
 ```
 
 ### Supported Version Formats