chore: support monorepo PWA linking w/ yarn link (OHIF#72)

Author: dannyrb

package.json

@@ -6,6 +6,7 @@
   "license": "MIT",
   "repository": "OHIF/react-vtkjs-viewport",
   "main": "dist/index.umd.js",
+  "module": "src/index.js",
   "engines": {
     "node": ">=8",
     "npm": ">=5"

postcss.config.js

@@ -0,0 +1,13 @@
+module.exports = function(ctx) {
+  ctx = ctx || {};
+  ctx.env = ctx.env || 'development';
+
+  return {
+    map: ctx.env === 'development' ? ctx.map : false,
+    plugins: {
+      'postcss-import': {},
+      'postcss-preset-env': {},
+      cssnano: ctx.env === 'production' ? {} : false,
+    },
+  };
+};