Move demo copying code to eleventy config
diff --git a/.eleventy.js b/.eleventy.js
index 7f4d70d..f8d7b69 100644
--- a/.eleventy.js
+++ b/.eleventy.js
@@ -4,6 +4,12 @@
     return JSON.stringify(input, null, '  ');
   });
 
+  eleventyConfig.addPassthroughCopy({
+    // '...relative to this file': '...relative to `dir.output` below'
+    'annotator/web/dist/demo/': 'demo/',
+    'annotator/web/dist/style.css': 'style.css'
+  });
+
   return {
     dir: {
       input: 'src',
diff --git a/package.json b/package.json
index 7ffa106..e1f1ff4 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,7 @@
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
     "build": "yarn run build:demo && eleventy",
-    "build:demo": "(cd annotator && yarn run web:build && cd ..) && rm -rf content/demo content/style.css && cp -r annotator/web/dist/demo content/demo && cp annotator/web/dist/style.css content/",
+    "build:demo": "cd annotator && yarn run web:build",
     "serve": "yarn run build:demo && eleventy --serve",
     "postinstall": "cd annotator && yarn install"
   },