[DOC] update tagging guidelines with squashing patch layers feature

[sozercan]

What kind of documentation improvement is needed?

Missing information or guidance

What is the change that is needed?

https://project-copacetic.github.io/copacetic/website/best-practices

this document references using unmodified images, we should update to include the new squashing patch layers feature

Are you willing to submit PRs to contribute to documentation?

• [ ] Yes, I am willing to implement it.