add support for podman chown volume mounting option

Podman supports a chown mounting feature ":U" that greatly simplifies running rootless containers. When trying to generate a quadlet I get the following error. Would you be willing to add support for this feature?
```
podlet compose compose.yaml
Error:
0: error converting compose file
1: error reading compose file
2: File `compose.yaml` is not a valid compose file
3: services.test.volumes[0]: unknown volume option `U` at line 7 column 9

Location:
src/cli/compose.rs:203
```

Example compose.yaml
```
services:
test:
image: docker.io/alpine:latest
user: 42
volumes:
- ./test:/test:U
```

Sidenote: volume mounting is broken in some crun versions, use stable (1.21) or latest (1.24+)