fix: use npm v8 in expressapp container to workaround slow npm instal…

…l from github

The switch to node v16 gets use npm v8, to workaround an issue with
slow 'npm install <any github repo dependency>'. See:
    npm/cli#4896

In our case the github repo dependency was the command given to docker
run this container:
    bash -c "npm install elastic-apm-node#SOME-COMMIT-SHA && node app.js"

This also adds a package.json to more explicitly declare we are working
with a node project workspace. Also avoid generating a package-lock file
we won't use.

Fixes: #1483

docker/nodejs/express/.npmrc

@@ -0,0 +1 @@
+package-lock=false

docker/nodejs/express/Dockerfile

@@ -1,8 +1,8 @@
-FROM node:12.18.1
+FROM node:16.15.0
 
 RUN mkdir -p /app
-RUN npm install express
-
-COPY app.js /app
+COPY package.json .npmrc app.js /app/
 
 WORKDIR /app
+RUN npm install
+

docker/nodejs/express/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "expressapp",
+  "version": "1.0.0",
+  "private": true,
+  "main": "app.js",
+  "dependencies": {
+    "express": "*"
+  }
+}