feat: add fuse-overlayfs storage driver for Docker-in-Docker

- Install fuse-overlayfs package in Dockerfile
- Configure Docker daemon to use fuse-overlayfs storage driver
- Add daemon.json configuration in entrypoint.sh
- Update documentation in README.md and README.es.md

This enables Docker-in-Docker to work efficiently in unprivileged
containers without requiring the overlay2 driver.

entrypoint.sh

@@ -91,6 +91,14 @@ mkdir -p "$HOME_DIR/.local/pipx/logs"
 chown -R "$DOCKER_USER:$DOCKER_USER" "$HOME_DIR/.local"
 chown -R "$DOCKER_USER:$DOCKER_USER" "$CONFIG_DIR"
 
+echo "[entrypoint] Configuring Docker daemon..."
+install -d -m755 /etc/docker
+cat > /etc/docker/daemon.json <<DOCKEREOF
+{
+  "storage-driver": "fuse-overlayfs"
+}
+DOCKEREOF
+
 echo "[entrypoint] Starting Docker daemon..."
 dockerd > /dev/null 2>&1 &