Use `node:18-alpine` instead of `node:18` to decrase docker image size

[alexander-mart]

node:18

node:18 based on buildpack-deps:bookworm ("Debian packages")

Dockerfile:
https://github.com/nodejs/docker-node/blob/ba2b3e61e6aaf4643108fb5f1cda9ee5238efde5/18/bookworm/Dockerfile

376.85 MB
https://hub.docker.com/layers/library/node/18/images/sha256-aa6c239d30ee04dede270729f9502389b1a9546687ce656872536340ee0a9e03

node:18-alpine

node:18-alpine based ib the Alpine Linux project. Alpine Linux is much smaller than most distribution base images (~5MB), and thus leads to much slimmer images in general.

Dockerfile:
https://github.com/nodejs/docker-node/blob/main/18/alpine3.21/Dockerfile

42.84 MB
https://hub.docker.com/layers/library/node/18-alpine/images/sha256-929b04d7c782f04f615cf785488fed452b6569f87c73ff666ad553a7554f0006

Additional info

• ⚠️ Actual version is node:lts-alpine3.21 (52.76 MB) with nodejs v22.15.0

• Reference: https://github.com/nodejs/docker-node?tab=readme-ov-file#nodeversion