Add comments for transforms (#16411)

scripts/build/transform/transforms/index.js

@@ -4,10 +4,18 @@ import transformObjectHasOwnCall from "./transform-object-has-own.js";
 import transformRelativeIndexing from "./transform-relative-indexing.js";
 import transformStringReplaceAll from "./transform-string-replace-all.js";
 
+// These transforms are like Babel and core-js
+// Allow us to use JavaScript features in our source code that are not yet
+// implemented in the Node.js version we support
+
 export default [
+  // Node.js 18.0.0
   transformArrayFindLast,
   transformArrayFindLastIndex,
+  // Node.js 16.9.0
   transformObjectHasOwnCall,
+  // Node.js 16.6.0
   transformRelativeIndexing,
+  // Node.js 15.0.0
   transformStringReplaceAll,
 ];