docs: add Long Term Support (LTS) README section

[MikeMcC399]

Description

Add LTS section to README.md

Motivation and Context

The README.md does not discuss lts and floating tags

LTS	Current
node:lts	node:current
node:lts-alpine	node:alpine
node:lts-bookworm	node:bookworm
node:lts-bullseye	node:bullseye
node:lts-trixie	node:trixie
node:lts-slim	node:slim

https://nodejs.org/en/about/previous-releases states

Production applications should only use Active LTS or Maintenance LTS releases.

Testing Details

N/A - documentation change only

Types of changes

• 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.

[nschonni]

Maybe this is more a subheading like https://github.com/nodejs/docker-node#nodeversion. Realizing that there is probably a missing similar explanation for the node:<codename>

[MikeMcC399]

Maybe this is more a subheading like https://github.com/nodejs/docker-node#nodeversion. Realizing that there is probably a missing similar explanation for the node:<codename>

I've added a new entry node:lts so that it follows the existing scheme. The full text is however kept separate, since the goal is to discuss the supportability aspects.

At some stage it would be worth considering restructuring the image variant section since it is difficult to extend. This addition is a bit of a compromise to add the supportability information for LTS without disturbing the rest of the text.

[MikeMcC399]

Preview

https://github.com/MikeMcC399/docker-node/blob/lts-tags/README.md#nodelts
https://github.com/MikeMcC399/docker-node/blob/lts-tags/README.md#long-term-support-lts

[sxa]

Approving regardless - will let others decide or comment on whether the LTS distinction should be changed.

[MikeMcC399]

Approving regardless - will let others decide or comment on whether the LTS distinction should be changed.

Thanks! I'll leave the PR open until beginning of next week though to allow for other feeback.