Making --use-root-maintainers available via CLI (#345)

It was reported that `--use-root-maintainers` is not explicitly
available via the CLI.

This PR should solved that, and close #344

src/bin/cli.ts

@@ -19,6 +19,11 @@ program
     'For every package.json found, generate a CODEOWNERS entry using the maintainers field',
     false
   )
+  .option(
+    '--use-root-maintainers',
+    'It will use `maintainers` field from the package.json in the root to generate default codeowners. Works only in conjunction with `useMaintainers`',
+    false
+  )
   .option(
     '--group-source-comments',
     'Instead of generating one comment per rule, enabling this flag will group them, reducing comments to one per source file. Useful if your codeowners file gets too noisy',