docs: add hint (#466)

Author: BioPhoton

packages/cli/README.md

@@ -77,7 +77,8 @@ _If you're looking for programmatic usage, then refer to the underlying [@code-p
 
 4. Run the CLI with `npx code-pushup` (see `--help` for list of commands and arguments).
 
-5. View report file(s) in output directory (specified by `persist.outputDir` configuration).
+5. View report file(s) in output directory (specified by `persist.outputDir` configuration).  
+   This folder should be ignored in your `.gitignore`.
 
 ### Set up categories (optional)