Warning about existing sites configs.

README.md

@@ -3,10 +3,12 @@
 After you make a fast web site, keep it fast by measuring it over time. Read [Use Speedlify to Continuously Measure Site Performance](https://www.zachleat.com/web/speedlify/). Created by [@zachleat](https://www.zachleat.com/).
 
 * Requires Node 12+
-* Each file in `_data/sites/*.js` is a category and contains a list of sites for comparison. I have a bunch of my own categories/sites in here but you’ll probably want to delete these files and create a `.js` file in that folder with a list of your own sites!
+* Each file in `_data/sites/*.js` is a category and contains a list of sites for comparison.
 
 ## Run locally
 
+_After cloning you’ll probably want to delete the initial `_data/sites/*.js` files and create your own file with a list of your own site URLs!_
+
 ```
 npm install
 npm run test-pages
@@ -17,6 +19,8 @@ npm run start
 
 Can run directly on Netlify (including your tests) and will save the results to a Netlify build cache (via Netlify Build Plugins, see `plugins/keep-data-cache/`).
 
+_After cloning you’ll probably want to delete the initial `_data/sites/*.js` files and create your own file with a list of your own site URLs!_
+
 <a href="https://app.netlify.com/start/deploy?repository=https://github.com/zachleat/speedlify"><img src="https://www.netlify.com/img/deploy/button.svg" width="146" height="32"></a>
 
 Speedlify will also save your data to `/results.zip` so that you can download later. Though this has proved to be unnecessary so far, it does serve as a fallback backup mechanism in case the Netlify cache is lost. Just look up your previous build URL and download the data to restore.