sw-precache: add comment for no fallback /api

Author: BDav24

Diff for: packages/react-scripts/config/webpack.config.prod.js

@@ -338,7 +338,7 @@ module.exports = {
       minify: true,
       // For unknown URLs, fallback to the index page
       navigateFallback: publicUrl + '/index.html',
-      // Ignores URLs starting from /__ (useful for Firebase):
+      // Ignores URLs starting from /api or /__ (useful for Firebase):
       // https://github.com/facebookincubator/create-react-app/issues/2237#issuecomment-302693219
       navigateFallbackWhitelist: [/^(?!\/(__|api)).*/],
       // Don't precache sourcemaps (they're large) and build asset manifest: