Update README with docker instructions. Reduce docker image size. Removed trailing whitespaces

Author: ba-tno

README.md

@@ -27,6 +27,17 @@ npm run build
 
 Learn more from the Create React App [README](https://github.com/facebook/create-react-app#npm-run-build-or-yarn-build) and [User Guide](https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md#deployment).
 
+## Docker ##
+To run this on a system without `make` and `node` you can use Docker.
+The provided `docker-compose.yml` file builds a Docker image from the latest master commit of the current repository, starts the server and exposes port 3000.
+
+To use it:
+
+```
+git clone --depth 1 https://github.com/magjac/graphviz-visual-editor
+cd graphviz-visual-editor
+docker-compose up -d
+```
 ## Implemented Features ##
 
 * Rendering of a graph from a textual [DOT](https://www.graphviz.org/doc/info/lang.html) representation.

docker-compose.yml

@@ -1,10 +1,10 @@
-version: "3.8"
+version: "3"
 services:
   graphviz-editor:
     build:
       context: ./docker
       dockerfile: Dockerfile
     container_name: graphviz-editor
     ports:
-      - "5000:5000"
-    restart: always
+      - "3000:3000"
+    restart: always

docker/Dockerfile

@@ -1,18 +1,33 @@
-FROM node:15.14.0-buster-slim
+# Multi-stage build to reduce final image size
+FROM node:lts-alpine3.15 as BUILD_IMAGE
 
-# Install git and install make
-RUN apt update 
-RUN apt install git -y
-RUN apt install make -y
+# Install git and make
+RUN apk update
+RUN apk add git
+RUN apk add make
 
 # Clone graphviz visual editor
 RUN git clone --depth 1 https://github.com/magjac/graphviz-visual-editor
 
 WORKDIR /graphviz-visual-editor
 
+# Install and make the dependencies
 RUN npm install
 RUN make
 RUN npm run build
+
+# Reduce the image size: remove development dependencies
+RUN npm prune --production
+
+# The stage that actually runs the application
+FROM node:lts-alpine3.15
+
+WORKDIR /graphviz-visual-editor
+
+# Copy the built artifacts from the build image
+COPY --from=BUILD_IMAGE /graphviz-visual-editor/build ./build
+COPY --from=BUILD_IMAGE /graphviz-visual-editor/node_modules ./node_modules
+
 RUN npm install -g serve
 
-CMD ["serve", "-s", "build"]
+CMD ["serve", "-s", "build"]