chore: update readme with example

Author: 43081j

README.md

@@ -15,11 +15,36 @@ npm i -D sourcemap-publisher
 npx sourcemap-publisher --provenance
 ```
 
-This will automatically detect which files you have in your `files` array
-(`package.json`), and will look up the sourcemaps for them.
+This will do the following:
 
-Once it has these, it will publish the package to npm under a `sourcemaps`
-tag and rewrite the sourcemap URLs to point to the external location.
+- Load the files in your `files` array in `package.json`
+- Find the sourcemaps any of these files reference
+- Package up these sourcemaps under `{packageName}@{version}-sourcemaps`
+- Rewrite the sourcemap URLs in the original sources to point at a CDN for
+this sourcemap package
+
+You should run this command **after your build**, but **before** you publish.
+
+## Example setup
+
+It is important to get the ordering right so you do not overwrite the
+rewritten sourcemap URLs.
+
+Generally, the order should be as follows:
+
+- Build your package
+- Run `sourcemap-publisher` to publish the sourcemaps and rewrite the URLs
+- Run `npm publish` to publish the rewritten sources
+
+You can achieve this through a `prepublishOnly` script in your `package.json`:
+
+```json
+{
+  "scripts": {
+    "prepublishOnly": "npm run build && sourcemap-publisher --provenance"
+  }
+}
+```
 
 ## Options