build(package.json): Set engines to node 8

To match the telus-isomorphic-starter-kit

package.json

@@ -5,13 +5,7 @@
   "license": "ISC",
   "main": "dist/tds.cjs.js",
   "module": "dist/tds.es.js",
-  "files": [
-    "dist",
-    "src",
-    "CHANGELOG.md",
-    "CONTRIBUTING.md",
-    "UPGRADING.md"
-  ],
+  "files": ["dist", "src", "CHANGELOG.md", "CONTRIBUTING.md", "UPGRADING.md"],
   "scripts": {
     "build:css": "postcss --use cssnano --replace dist/tds.css",
     "build:js": "rollup -c config/rollup.config.js",
@@ -25,11 +19,13 @@
     "dev": "styleguidist server --config config/styleguide.config.js",
     "gitbook": "gitbook serve guide",
     "gitbook:install": "gitbook install guide",
-    "lint:js": "eslint src config docs scripts --ext '.js,.jsx' --config config/.eslintrc.json --fix",
+    "lint:js":
+      "eslint src config docs scripts --ext '.js,.jsx' --config config/.eslintrc.json --fix",
     "lint:scss": "stylelint 'src/components/**/*.scss' --config config/.stylelintrc.json",
     "lint:ec": "echint",
     "lint": "yarn lint:js && yarn lint:scss && yarn lint:ec",
-    "precommit": "yarn lint && yarn test && yarn build-package && yarn build-styleguide && yarn build-gitbook",
+    "precommit":
+      "yarn lint && yarn test && yarn build-package && yarn build-styleguide && yarn build-gitbook",
     "release:changelog": "changelog",
     "release": "scripts/release.sh",
     "scaffold": "node scripts/scaffold.js",
@@ -43,6 +39,9 @@
     "url": "git+https://github.com/telusdigital/tds.git"
   },
   "author": "TELUS Digital",
+  "engines": {
+    "node": ">=8"
+  },
   "bugs": {
     "url": "https://github.com/telusdigital/tds/issues"
   },