[docker-outside-of-docker] Update default `dockerDashComposeVersion` to latest and update documentation

[hiro345g]

Description

Currently, the docker-outside-of-docker feature installs a relatively old version of Docker Compose by default. I would like to propose updating the default version to the latest (v5+) and updating the documentation to clarify that latest is a valid option for dockerDashComposeVersion.

Current Behavior

When using the default settings, Docker Compose version v2.40.3 is installed.
According to the documentation, only v1, v2, and none are listed as valid options for dockerDashComposeVersion.

Verification Results

I have verified that specifying latest works correctly and installs the current major version (v5).

1. Default configuration (Standard):

"features": {
  "ghcr.io/devcontainers/features/docker-outside-of-docker:1": {}
}

Result: Docker Compose version v2.40.3

2. Specifying latest:

"features": {
  "ghcr.io/devcontainers/features/docker-outside-of-docker:1": {
    "dockerDashComposeVersion": "latest"
  }
}

Result: Docker Compose version v5.0.2

Proposed Changes

I would appreciate it if you could consider the following updates:

1. Update Default: Set the default value of dockerDashComposeVersion to latest so users can benefit from the most recent features and security updates.
2. Update Documentation: Add latest to the list of supported values for dockerDashComposeVersion in the feature's README.md or devcontainer-feature.json.