created Dockerfile and entrypoint with default http port

Dockerfile

@@ -0,0 +1,15 @@
+FROM node:alpine as builder
+RUN apk update && apk add --no-cache python make g++
+WORKDIR /opt/app/
+COPY package.json ./
+RUN npm install
+RUN npm prune
+
+FROM node:alpine as webapp
+RUN apk add curl
+WORKDIR /opt/app
+COPY . /opt/app
+COPY --from=builder /opt/app/node_modules ./node_modules
+COPY ./entrypoint.sh /entrypoint.sh
+RUN chmod +x /entrypoint.sh
+ENTRYPOINT ["/entrypoint.sh"]

entrypoint.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+PUBLIC_IPV4="$(curl --fail -qs whatismyip.akamai.com)"
+API_PORT="${API_PORT:-3000}"
+API_VERSION="${API_VERSION:-v1}"
+echo "REACT_APP_API_BASE_URL=${REACT_APP_API_BASE_URL:-http://$PUBLIC_IPV4}:$API_PORT/$API_VERSION" > /opt/app/.env
+cd /opt/app/
+npm run build
+npm run serve

package.json

@@ -15,11 +15,11 @@
     "styled-components": "^5.0.1"
   },
   "scripts": {
-    "start": "PORT=3001 react-scripts start",
+    "start": "PORT=${HTTP_PORT:-3001} react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject",
-    "serve": "serve -s build -l 3001",
+    "serve": "serve -s build -l ${HTTP_PORT:-3001}",
     "pm2": "pm2 start npm --name \"jambonz-webapp\" -- run serve",
     "deploy": "npm i && npm run build && npm run pm2"
   },