Update reference variables (othneildrew#39)

The reference variables at the bottom of the file use "repo" instead of "repo_name". It causes to retype the repo name too many times.

BLANK_README.md

@@ -185,14 +185,14 @@ Project Link: [https://github.com/github_username/repo_name](https://github.com/
 <!-- MARKDOWN LINKS & IMAGES -->
 <!-- https://www.markdownguide.org/basic-syntax/#reference-style-links -->
 [contributors-shield]: https://img.shields.io/github/contributors/github_username/repo.svg?style=for-the-badge
-[contributors-url]: https://github.com/github_username/repo/graphs/contributors
+[contributors-url]: https://github.com/github_username/repo_name/graphs/contributors
 [forks-shield]: https://img.shields.io/github/forks/github_username/repo.svg?style=for-the-badge
-[forks-url]: https://github.com/github_username/repo/network/members
+[forks-url]: https://github.com/github_username/repo_name/network/members
 [stars-shield]: https://img.shields.io/github/stars/github_username/repo.svg?style=for-the-badge
-[stars-url]: https://github.com/github_username/repo/stargazers
+[stars-url]: https://github.com/github_username/repo_name/stargazers
 [issues-shield]: https://img.shields.io/github/issues/github_username/repo.svg?style=for-the-badge
-[issues-url]: https://github.com/github_username/repo/issues
+[issues-url]: https://github.com/github_username/repo_name/issues
 [license-shield]: https://img.shields.io/github/license/github_username/repo.svg?style=for-the-badge
-[license-url]: https://github.com/github_username/repo/blob/master/LICENSE.txt
+[license-url]: https://github.com/github_username/repo_name/blob/master/LICENSE.txt
 [linkedin-shield]: https://img.shields.io/badge/-LinkedIn-black.svg?style=for-the-badge&logo=linkedin&colorB=555
 [linkedin-url]: https://linkedin.com/in/github_username