Ensure lint container file are owned by host user

Same as the test container.

It's working fine locally but not in GHA:

npm ERR! Error: EACCES: permission denied, rename '/app/node_modules/@eslint-community/regexpp' -> '/app/node_modules/@eslint-community/.regexpp-MJHcVchs'

I think/guess it's because the lint and test containers share
node_modules (by volume) and npm can see that there is already stuff in
there that was installed by a different version of node, so is trying to
move it. All a bit gross, but hopefully this will sort it for now.

Author: c24w

docker-compose.yml

@@ -4,6 +4,11 @@ services:
     volumes:
       - .:/app
     working_dir: /app
+    entrypoint: |-
+      sh -ceuo pipefail '
+        apk add shadow
+        usermod -u $HOST_UID node
+        su node -c "$$@"'
     command: sh -c 'npm i --no-save eslint && ./node_modules/.bin/eslint --color .'
 
   test: &test