Add a dockerfile, document its usage in the readme (#260)

Dockerfile

@@ -0,0 +1,13 @@
+FROM node:buster
+
+RUN apt-get update -y \
+ && apt-get install -y --no-install-recommends \
+    bundler \
+    ruby \
+    ruby-dev \
+    \
+    fontforge \
+    woff-tools \
+    woff2
+
+CMD bash

README.md

@@ -88,6 +88,27 @@ Or serve it on a local server on http://localhost:7998:
 
     $ npm run dev
 
+### Build the font in a Docker container
+
+Another possibility is to build the font using the Dockerfile provided.
+
+First, build the Docker image:
+
+    $ docker build -t fa-builder .
+
+Then, run the Docker container:
+
+    $ docker run --rm -it \
+        -u $(id -u):$(id -g) \
+        -v $(pwd):$(pwd) \
+        -w $(pwd) \
+        fa-builder
+
+Within the container, build the font:
+
+    $ bundle install --path vendor/bundle
+    $ npm ci
+    $ make -C src/icons
 
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