Add a Dockerfile

Build an image from this `Dockerfile`, start a container with appropriate `-v` and `-p`, and shell into it, and don't worry about trying to get ruby 2.7 or yarn installed locally :)

.dockerignore

@@ -0,0 +1 @@
+*

Dockerfile

@@ -0,0 +1,8 @@
+FROM ruby:2.7
+
+RUN curl -fsSL https://deb.nodesource.com/setup_lts.x | bash -\
+  && apt-get update \
+  && apt-get install -y nodejs \
+  && npm install --global yarn \
+  && gem install bundler:1.16.2
+

package.json

@@ -9,7 +9,7 @@
     "coverage": "node_modules/.bin/jest --coverage",
     "checkdata": "if [ ! -d \"data\" ]; then yarn parse; fi && if [ ! -d \"src/_data\" ]; then yarn parse:catalog; fi",
     "build": "yarn parse && yarn parse:catalog && bundle exec jekyll clean && bundle exec jekyll build && node_modules/.bin/webpack -p --mode production",
-    "dev": "yarn checkdata && yarn concurrently \"node_modules/.bin/webpack --mode development --watch\" \"bundle exec jekyll serve\"",
+    "dev": "yarn checkdata && yarn concurrently \"node_modules/.bin/webpack --mode development --watch\" \"bundle exec jekyll serve -H ${HOST:-127.0.0.1}\"",
     "lint": "node_modules/.bin/eslint webpack/**/*.{js,jsx} webpack/*.{js,jsx} --quiet",
     "precommit": "lint-staged",
     "parse": "./node_modules/babel-cli/bin/babel-node.js ./webpack/scripts/parser.js",