build: Add script to build `dist/icons.json`

.babelrc

+{
+  "presets": [
+    "es2015"
+  ]
+}

Makefile

+node_modules:
+	npm install
+
+dist:
+	mkdir dist
+
+dist/icons.json: node_modules dist icons icons/*.svg
+	./node_modules/.bin/babel-node bin/build-json.js

bin/build-json.js

+/**
+ * @file Builds `icons.json` from `icons` directory.
+ */
+
+/* eslint-disable import/no-extraneous-dependencies */
+import fs from 'fs';
+import path from 'path';
+import RSVP from 'rsvp';
+import Svgo from 'svgo';
+import parse5 from 'parse5';
+
+const svgFiles = fs.readdirSync(path.resolve(__dirname, '../icons'))
+  .filter(file => path.extname(file) === '.svg');
+
+buildIconsObject(svgFiles)
+  .then(icons => {
+    fs.writeFileSync(
+      path.resolve(__dirname, '../dist/icons.json'),
+      JSON.stringify(icons),
+    );
+  });
+
+/**
+ * Build an icons object in the format: `{ <icon name>: <svg content> }`.
+ * @param {string[]} svgFiles - A list of file names.
+ * @returns {RSVP.Promise<Object>}
+ */
+function buildIconsObject(svgFiles) {
+  const icons = {};
+
+  svgFiles.forEach(svgFile => {
+    const svg = fs.readFileSync(path.resolve(__dirname, '../icons', svgFile), 'utf8');
+    const key = path.basename(svgFile, '.svg');
+
+    icons[key] = optimizeSvg(svg)
+      .then(optimizedSvg => getSvgContent(optimizedSvg));
+  });
+
+  return RSVP.hash(icons);
+}
+
+/**
+ * Optimize SVG with `svgo`.
+ * @param {string} svg - An SVG string.
+ * @returns {RSVP.Promise<string>}
+ */
+function optimizeSvg(svg) {
+  // configure svgo
+  const svgo = new Svgo({
+    plugins: [
+      { convertShapeToPath: false },
+      { mergePaths: false },
+      { removeAttrs: { attrs: '(fill|stroke.*)' } },
+    ],
+  });
+
+  return new RSVP.Promise(resolve => {
+    svgo.optimize(svg, ({ data }) => resolve(data));
+  });
+}
+
+/**
+ * Get content between opening and closing `<svg>` tags.
+ * @param {string} svg - An SVG string.
+ * @returns {string}
+ */
+function getSvgContent(svg) {
+  const fragment = parse5.parseFragment(svg);
+  const content = parse5.serialize(fragment.childNodes[0]);
+  return content;
+}