Add Node debian core variant

[LaurentGoderre]

Add debian core variant without npm or yarn

• Documentation
• Version change (Update, remove or add more Node.js versions)
• Variant change (Update, remove or add more variants, or versions of variants)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other (none of the above)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING.md document.
• All new and existing tests passed.

[LaurentGoderre]

Note to reviewer, only check the top commit since the other one is the security update. I rebased on top of it to validate it would work when the base image (the slim variant) didn't already exist.

[PeterDaveHello]

Do we also need an opinion from @tianon?

[tianon]

"slim" is already an established convention in official images (with some slight variance for whether it's "FROM slim" or a slimmed image itself), but "core" is not, so I wonder if "core" is already established nomenclature in Node.js communities?

Also, I think it's probably worth updating the templating to not copy docker-entrypoint.sh (which is copied from the "donor" image, not from the build context).

[LaurentGoderre]

We are but painted into a corner because slim already contain package manager so we need a different name.

Why not copy the entry point? Do you think it's better to copy from file?

[tianon]

Well, the Dockerfile as written is already copying the entrypoint from the donor image (which is fine, I think), so having it in the build context again is unnecessary and just makes the diff larger without a real purpose. 😄

[LaurentGoderre]

Fixed