Feature and motivation

Referencing #1401 and considering the new Docker Hub rate limit restrictions, it might be a good idea to publish the images to both Docker Hub and GHCR.

• GHCR provides faster pulls with no rate limits.
• Existing users can continue using Docker Hub without changes.
• Users who prefer GHCR only need to prefix with ghcr.io/selenium/....

This dual publishing strategy would give the community more flexibility and resilience against Docker Hub limitations.

Usage example

Users who prefer GHCR could simply pull images like this:

docker pull ghcr.io/selenium/standalone-chrome:latest
docker run -d -p 4444:4444 ghcr.io/selenium/standalone-chrome:latest

This avoids Docker Hub rate limits while keeping compatibility for those still pulling from Docker Hub.