X11/GPU container support for containers in README

[j-rivero]

This pull request significantly improves the README.md documentation to better guide users in running Gazebo containers with GPU and display support across a variety of OCI-compatible tools. The updates clarify the recommended starting point for new users, provide detailed usage instructions for multiple container runtimes, and enhance the overall structure and accessibility of the documentation.

Major documentation improvements:

• Recommends rocker as the preferred starting point for new users, emphasizing its automatic GPU and display setup, and provides updated installation and usage instructions.
• Expands and restructures the section on using Gazebo images with alternative OCI-compatible tools, adding detailed, tool-specific instructions (including GPU and X11 support), example commands, and links to relevant documentation for: Apptainer, Distrobox, nerdctl, Podman, Rocker, Sarus, and SingularityCE.

[j-rivero]

@copilot fix the linting

[Copilot]

@j-rivero I've opened a new pull request, #5, to work on those changes. Once the pull request is ready, I'll request review from you.