add to disable csspurging on production

see http://notes.gugelfrei.de/#root/CJy29hue71WM/HmK2rsbse12W-4KEq

postcss.config.js

@@ -0,0 +1,38 @@
+const removeNewlines = (string) => string.replace(/\n$/g, "");
+
+// See https://gohugo.io/hugo-pipes/postprocess/#css-purging-with-postcss
+const purgecss = require("@fullhuman/postcss-purgecss")({
+  content: [
+    //
+    // TODO: Maybe use process.cwd() to get some heuristics of what
+    // is going on, i.e. which of the following cases we are in.
+    //
+
+    // When this file is copied to the root of your Hugo site
+    "./hugo_stats.json",
+    // When your Hugo site does not have its own postcss.config.js
+    // and hence this file is used inside ./themes/hugo-product-launch
+    "../../hugo_stats.json",
+    // When building the exampleSite during development
+    "./exampleSite/hugo_stats.json",
+  ],
+  defaultExtractor: (content) => {
+    let els = JSON.parse(content).htmlElements;
+    // An HTML element-name may include a newline, e.g.
+    // <a
+    //    href="https://www.yo.com"
+    //    class="pretty-link"
+    // >Yo!</a>
+    // Thus we remove those newlines.
+    return els.tags.concat(els.classes, els.ids).map(removeNewlines);
+  },
+});
+
+module.exports = {
+  plugins: [
+    require("postcss-import"),
+    require("tailwindcss"),
+    require("autoprefixer"),
+    // ...(process.env.HUGO_ENVIRONMENT === "production" ? [purgecss] : []),
+  ],
+};