Include a Dockerfile and instructions.

.dockerignore

@@ -0,0 +1 @@
+node_modules

Dockerfile

@@ -0,0 +1,16 @@
+FROM node:12
+# docker build -t sourcecred-widgets .
+
+# Set up working directory.
+RUN mkdir -p /code
+WORKDIR /code
+
+# Install global and local dependencies first so they can be cached.
+RUN npm install -g yarn@^1.17
+COPY package.json yarn.lock /code/
+RUN yarn
+
+# Install the remainder of our code.
+COPY . /code
+
+ENTRYPOINT ["/code/bin/contributor-wall-svg.js"]

README.md

@@ -12,13 +12,31 @@ For example to use in README's or as webpage static assets.
 
 ```sh
 # 1. Use the main sourcecred's score feature to export scores to a file.
-export SOURCECRED_GITHUB_TOKEN=YOUR_GITHUB_TOKEN
-node PATH_TO_SOURCECRED/bin/sourcecred.js load sourcecred/sourcecred
+SOURCECRED_GITHUB_TOKEN=YOUR_GITHUB_TOKEN \
+	node PATH_TO_SOURCECRED/bin/sourcecred.js load sourcecred/sourcecred
 node PATH_TO_SOURCECRED/bin/sourcecred.js scores sourcecred/sourcecred > scores.json
 
 # 2. Install this package's dependencies.
 yarn
 
 # 3. Generate a contributor wall SVG.
-./bin/contributor-wall-svg.js < scores.json > contributors.svg
+SOURCECRED_GITHUB_TOKEN=YOUR_GITHUB_TOKEN \
+	./bin/contributor-wall-svg.js < scores.json > contributors.svg
+```
+
+Or using the Docker equivalent of this.
+
+```sh
+# 1. Use the main sourcecred image to export scores to a file.
+SOURCECRED_GITHUB_TOKEN=YOUR_GITHUB_TOKEN \
+	docker run --rm -ti -v sourcecred_data:/data -e SOURCECRED_GITHUB_TOKEN sourcecred/sourcecred load sourcecred/sourcecred
+docker run --rm -ti -v sourcecred_data:/data sourcecred/sourcecred scores sourcecred/sourcecred > scores.json
+
+# 2. To build a Docker image with your changes. Or skip this to use a release from Dockerhub.
+docker build -t sourcecred/widgets .
+
+# 3. Generate a contributor wall SVG.
+# Note: don't use the -t option here, it will produce an error "the input device is not a TTY".
+SOURCECRED_GITHUB_TOKEN=YOUR_GITHUB_TOKEN \
+	docker run --rm -i -e SOURCECRED_GITHUB_TOKEN sourcecred/widgets < scores.json > contributors.svg
 ```