docs: added in docs supported webpack version (#1305)

Author: cap-Bernardito

README.md

@@ -21,6 +21,8 @@ The `css-loader` interprets `@import` and `url()` like `import/require()` and wi
 
 ## Getting Started
 
+> ⚠ To use css-loader, webpack@5 is required
+
 To begin, you'll need to install `css-loader`:
 
 ```console