Documentation and logistics update

• Updates README.md with a link to the DockerHub project.
• Updates .gitignore to filter out mapped volumes used for SDK Manager downloading and image generation.

v1.0.0

Initial commit and release of a working Docker container based on Ubuntu 20.04 LTS that properly executes the NVIDIA SDK Manager with X11 forwarding to the host and successfully flashes the NVIDIA Jetson Orin AGX 64GB dev kit.