Add NodeJS 21

[rumenbl]

Description

This PR adds NodeJS 21. I checked and saw no other pull requests regarding node 21, decided to create one using the 21-bullseye-slim tag like the dockerfile for node20 was using, just 21-bullseye-slim not 20-bullseye-slim

All Submissions:

• [x] Have you ensured there aren't other open Pull Requests for the same update or change?
• [x] Have you created a new branch for your changes and PR from that branch and not from your master branch?

New Image Submissions:

1. [x] Have you added your image to the Github workflows?
2. [x] Have you updated the README list to contain your new image?