feat: add pure bundle build (#489)

Closes #486

Author: Kent C. Dodds

package.json

@@ -8,7 +8,11 @@
     "node": ">=8"
   },
   "scripts": {
-    "build": "kcd-scripts build && kcd-scripts build --bundle --no-clean",
+    "prebuild": "rimraf dist",
+    "build": "npm-run-all --parallel build:main build:bundle:main build:bundle:pure",
+    "build:main": "kcd-scripts build --no-clean",
+    "build:bundle:main": "kcd-scripts build --bundle --no-clean",
+    "build:bundle:pure": "cross-env BUILD_FILENAME_SUFFIX=.pure BUILD_INPUT=src/pure.js kcd-scripts build --bundle --no-clean",
     "lint": "kcd-scripts lint",
     "test": "kcd-scripts test",
     "test:update": "npm test -- --updateSnapshot --coverage",
@@ -48,9 +52,12 @@
   "devDependencies": {
     "@reach/router": "^1.2.1",
     "@testing-library/jest-dom": "^4.1.0",
+    "cross-env": "^6.0.0",
     "kcd-scripts": "^1.7.0",
+    "npm-run-all": "^4.1.5",
     "react": "^16.9.0",
-    "react-dom": "^16.9.0"
+    "react-dom": "^16.9.0",
+    "rimraf": "^3.0.0"
   },
   "peerDependencies": {
     "react": "*",