fix: address review feedback

- Update docs/index.md browser support table to reflect dropped IE 11
- Add comment to .babelrc explaining retained modules-commonjs plugin
- Expand changeset with migration guidance for affected users

Co-Authored-By: Claude <noreply@anthropic.com>

Author: kdaviduik

.babelrc

@@ -7,6 +7,7 @@
   ],
   "env": {
     "development": {
+      // Retained for Browserify/testem test pipeline — removed in PR 7a when Vitest replaces Browserify
       "plugins": [
         "@babel/plugin-transform-modules-commonjs"
       ]

.changeset/drop-ie11-modernize-targets.md

@@ -3,3 +3,8 @@
 ---
 
 Drop IE 11, Safari 8, iOS 8, Android 4.4 browser support. Minimum browser targets are now rolling modern versions aligned with Shopify Online Store themes. The library now emits ES2015+ JavaScript (native classes, arrow functions, template literals) and no longer transpiles to ES5.
+
+**Migration guide:**
+- If you need IE 11 support, pin to `@shopify/buy-button-js@^3.0.0`.
+- If you use the CDN `latest` URL (`sdks.shopifycdn.com/buy-button/latest/buybutton.js`), pin to a specific 3.x version before upgrading.
+- If your site relied on buy-button-js to provide `fetch`, `Promise`, or ES6 array/object polyfills as a side effect, you must now provide your own polyfills.

docs/index.md

@@ -17,9 +17,11 @@ This tool is intended for use by developers who are familiar with JavaScript and
 
 ## Current Support
 
-| Internet Explorer     | Chrome, Edge, Firefox, Opera     | Safari    | iOS     | Android   |
-| :-------------------- | :------------------------------- | :-------- | :------ | :-------- |
-| 11+                   | (Current - 1) or Current         | 8+        | 8+      | 4.4+
+| Chrome | Firefox | Safari | Edge | iOS | Android |
+| :----- | :------ | :----- | :--- | :-- | :------ |
+| Last 3 | Last 3  | Last 3 | Last 3 | 13.4+ | Last 3 Chrome |
+
+> **Note (v4.0.0+):** Internet Explorer, Safari 8, iOS 8, and Android 4.4 are no longer supported. If you need IE 11 support, pin to v3.x.
 
 ## Including the library