Add Dockerfile to serve documentation

Use a container to preview the documentation for those of us who cannot or do not want to install npm/nodejs on their machines.

- Add a Dockefile to create a docker image containing nodejs and the software needed to serve the documentation
- Extend README.md with the option to use the Dockerfile to preview the documentation

Dockerfile

@@ -0,0 +1,15 @@
+FROM node:12.22.12-stretch-slim
+
+RUN apt-get update && apt-get -y upgrade
+
+RUN apt-get install -y git
+
+RUN mkdir /opt/documentation && chown node: /opt/documentation
+
+USER node
+
+WORKDIR /opt/documentation
+
+RUN npm install
+
+CMD [ "npm", "run", "serve"]

README.md

@@ -32,6 +32,39 @@ should automatically reload all changed pages using the amazing Browsersync.
 When you're done, commit your changes to your fork and write a pull request for
 Codeberg/Documentation. We're happy about every contribution!
 
+### Local development using the Dockerfile
+
+If you do not have nodejs installed or do not want to run the development web server directly on your host,
+you can also use a docker container.
+
+You must have a container-engine installed (docker, podman, etc.)
+
+First build the container image:
+
+```shell
+docker build -t codeberg/documentation-server .
+```
+
+You do not have to rebuild the image every time. Once you build the image you can always start the development
+webserver using the container engine:
+
+```shell
+docker run --rm -v $PWD/opt/documentation codeberg/documentation-server:latest
+```
+
+Use the "External" URL the container outputs on startup to access your documentation.
+
+Changes to files in the documentation are reflected in the browser as the server regularly updates the generated files.
+
+Use `Ctrl-C` to exit / end the container.
+
+The parameters are:
+
+`--rm` removes the container after it's use
+`-v` mounts the current (documentation repository root) folder to `/opt/documentation` in the container.
+
+`codeberg/documentation-server:latest` refers to the container image built in the first step (using `docker build`).
+
 ### Build & Deployment
 Like for local development, before building and deploying you first have to install
 the dependencies (once):