Update Docker examples

[NatoBoram]

As of Node.js 25, the example Dockerfiles at https://pnpm.io/docker are outdated.

 => ERROR [base 2/4] RUN corepack enable                                               0.7s
------
 > [base 2/4] RUN corepack enable:
0.305 /bin/sh: 1: corepack: not found
------
Dockerfile:4
--------------------
   2 |     ENV PNPM_HOME="/pnpm"
   3 |     ENV PATH="$PNPM_HOME:$PATH"
   4 | >>> RUN corepack enable
   5 |     COPY . /app
   6 |     WORKDIR /app
--------------------
ERROR: failed to build: failed to solve: process "/bin/sh -c corepack enable" did not complete successfully: exit code: 127
 ELIFECYCLE  Command failed with exit code 1.
 ELIFECYCLE  Command failed with exit code 1.

In the changelogs at https://nodejs.org/en/blog/release/v25.0.0, we can see a bunch of entries about Corepack:

• [f31c88021b] - (SEMVER-MAJOR) build: stop distributing Corepack (Antoine du Hamel) #57617
• [22a864a275] - build: remove corepack from release tarballs (Jordan Harband) #59835
• [86bfdb5528] - build: remove nocorepack vcbuild flag (Antoine du Hamel) #57772

From In a Docker container, the instructions should probably be updated to something like:

FROM node:25-slim AS base
ENV PNPM_HOME="/pnpm"
ENV PATH="$PNPM_HOME:$PATH"
RUN apt update && apt install --yes wget && rm -rf /var/lib/apt/lists/*
RUN wget -qO- https://get.pnpm.io/install.sh | ENV="$HOME/.bashrc" SHELL="$(which bash)" bash -