Add docker and run-docker make targets.

This enables testing the website locally as follows:

1. Run `make docker`
2. Run `make run-docker`
3. Navigate to http://localhost:5002

Makefile

@@ -4,20 +4,31 @@ default: help
 .PHONY: help
 help:
 	@echo "make help              Show this help message"
-	@echo "make dev               Run the pattern library app in a development server"
 	@echo "make build             Build the package"
-	@echo "make lint              Run the code linter(s) and print any warnings"
 	@echo "make checkformatting   Check code formatting"
+	@echo "make clean             Delete development artefacts (cached files etc.)"
+	@echo "make dev               Run the pattern library app in a development server"
+	@echo "make docker            Build Docker image for the website"
 	@echo "make format            Automatically format code"
-	@echo "make test              Run the unit tests once"
+	@echo "make lint              Run the code linter(s) and print any warnings"
+	@echo "make run-docker        Run a Docker container using the image created by \`make docker\`"
 	@echo "make sure              Make sure that the formatter, linter, tests, etc all pass"
-	@echo "make clean             Delete development artefacts (cached files, "
-	@echo "                       dependencies, etc)"
+	@echo "make test              Run the unit tests once"
 
 .PHONY: dev
 dev: node_modules/.uptodate
 	node_modules/.bin/gulp watch
 
+.PHONY: docker
+docker:
+	@git archive --format=tar.gz HEAD | docker build -t hypothesis/frontend-shared:latest -
+
+# Run Docker container. Publish to port 5002 on the host to avoid a conflict
+# with other Hypothesis projects.
+.PHONY: run-docker
+run-docker:
+	@docker run --rm -p 5002:5001 --name hypothesis-frontend-shared hypothesis/frontend-shared:latest
+
 .PHONY: test
 test: node_modules/.uptodate
 ifdef ARGS