chore(prettier): add prettier

.prettierignore

@@ -0,0 +1,34 @@
+*.min.js
+**/node_modules/**
+flow-typed
+
+# webfont demo styles
+**/specimen_files
+
+# built sites
+benchmarks/**/public
+e2e-tests/**/public
+examples/**/public
+integration-tests/**/public
+www/public
+
+# cache-dirs
+**/.cache
+
+# ignore built packages
+packages/**/*.js
+!packages/gatsby/cache-dir/**/*.js
+!packages/*/src/**/*.js
+packages/gatsby/cache-dir/commonjs/**/*.js
+
+# fixtures
+**/__testfixtures__/**
+**/__tests__/fixtures/**
+
+infrastructure
+
+# coverage
+coverage
+
+# forestry files
+.forestry/**/*

.prettierrc.js

@@ -0,0 +1,19 @@
+module.exports = {
+	endOfLine: 'lf',
+	semi: true,
+	singleQuote: true,
+	useTabs: true,
+	trailingComma: 'es5',
+	overrides: [
+		{
+			// This file uses semicolons. It's needed here because `documentation`
+			// package (used to parse jsdoc and provide content for API reference pages)
+			// behaviour is inconsistent when not using semicolons after
+			// object declarations.
+			files: ['**/api-node-helpers-docs.js'],
+			options: {
+				semi: true,
+			},
+		},
+	],
+}

package.json

@@ -32,7 +32,8 @@
     "major": "release major"
   },
   "dependencies": {
-    "eslint-plugin-sort-class-members": "^1.0.1"
+    "eslint-plugin-sort-class-members": "^1.0.1",
+    "prettier": "^1.18.2"
   },
   "peerDependencies": {
     "eslint": ">=0.8.0"