docs: Correct pnpm installation syntax

MichalBryxi · web-flow · commit c5c4ea0af36a · 2025-07-22T16:33:35.000+02:00
diff --git a/README.md b/README.md
@@ -20,7 +20,7 @@ Installation
 
 #### pnpm
 ```bash
-pnpm add --dev @ember/test-helpers
+pnpm add --save-dev @ember/test-helpers
 ```
 
 #### npm
