📝 document the local dev process

README.md

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 A website for [perf.email](https://perf.email/): an up-to-date web platform news email to make you a better performance advocate.
 
 Made by the team at [♠ Calibre](https://calibreapp.com/), your performance companion.
+
+## Initial installation
+
+`npm install`
+
+## Running the project
+
+`npm run dev` launches a local Vite dev server, accessible via [http://127.0.0.1:5173/](http://127.0.0.1:5173/). 
+
+Vite’s dev server watches for source file changes, performing a live reload if any are detected.
+
+## Build and preview
+
+The `npm run build` command generates production build files, output to the `/dest` directory. 
+
+To preview the build files locally, run the `npm run preview` command.
+
+## RSS feed
+
+`api/rss.js` leverages [Vercel’s serverless function](https://vercel.com/docs/concepts/functions/serverless-functions) capability to perform an on-demand request of [perf.email](https://perf.email/) issues from Mailchimp, returned as an RSS XML file. 
+
+The `MAILCHIMP_API_KEY` environment variable is required for the Mailchimp API call.