Add prettier (closes #1)

Install prettier globally beside wrangler and wrangler's peers, and
check it in the smoke test. prettier ships no distro package for
Ubuntu, so npm global is the standard install.

Model: deepseek-v4-pro

README.md

@@ -27,6 +27,7 @@ Image: `git.eeqj.de/sneak/baseimage`, built for `linux/amd64` and
 | corepack        | `npm install -g corepack`      | nvm LTS global bin             |
 | yarn, pnpm      | corepack, cache pre-populated  | `/usr/local/corepack`          |
 | wrangler        | `npm install -g wrangler`      | nvm LTS global bin             |
+| prettier        | `npm install -g prettier`      | nvm LTS global bin             |
 | Python (distro) | apt `python3`, `pip`, `venv`   | `/usr/bin/python3`             |
 | pyenv           | git tag                        | `/usr/local/pyenv`             |
 | Python (latest) | `pyenv install`                | `/usr/local/pyenv/versions/*`  |

bin/test

@@ -20,6 +20,7 @@ docker run --rm "$img" bash -ec '
     go version; node --version; python3 --version; hugo version | head -1
     COREPACK_ENABLE_NETWORK=0 yarn --version
     COREPACK_ENABLE_NETWORK=0 pnpm --version
+    prettier --version
 '
 
 echo "== $img: runit service lifecycle"

build.sh

@@ -61,7 +61,7 @@ nvm install --lts
 nvm alias default "lts/*"
 nvm use default
 set -ux
-npm install -g npm@latest corepack wrangler
+npm install -g npm@latest corepack wrangler prettier
 corepack enable
 # Pre-populate the corepack cache so projects that pin a package manager
 # do not download at run time. The last yarn installed becomes the default.
@@ -102,6 +102,7 @@ npm --version
 COREPACK_ENABLE_NETWORK=0 yarn --version
 COREPACK_ENABLE_NETWORK=0 pnpm --version
 wrangler --version
+prettier --version
 python3 --version
 pip --version
 virtualenv --version