docs: update example in README.md

Author: koyashiro

Diff for: README.md

@@ -9,5 +9,5 @@ cargo install --locked --git https://github.com/koyashiro/vpm-repos-gen
 ## Example
 
 ```sh
-vpm-repos-gen --name "koyashiro" --author 'koyashiro' --url 'https://vpm.koyashiro.net/repos.json' --repos 'koyashiro/udon-list' --repos 'koyashiro/udon-dictionary'
+vpm-repos-gen --name "koyashiro" --author 'koyashiro' --url 'https://vpm.koyashiro.net/repos.json' --repos 'koyashiro/udon-list,koyashiro/udon-dictionary'
 ```