docs: add codecov badge to README

README.md

@@ -2,6 +2,7 @@
 
 [![npm version][npm-version-src]][npm-version-href]
 [![npm downloads][npm-downloads-src]][npm-downloads-href]
+[![codecov][codecov-src]][codecov-href]
 [![License][license-src]][license-href]
 
 A utility library offering easy-to-use HTTP request wrappers, secure hash functions, flexible logging, datetime utilities, and more to simplify Node.js development.
@@ -115,11 +116,14 @@ Some functions or the top of files will have related comments and examples.
 [MIT License](./LICENSE)
 
 <!-- Badges -->
-[npm-version-src]: https://img.shields.io/npm/v/@kikiutils/node/latest.svg?style=flat&colorA=18181B&colorB=28CF8D
 [npm-version-href]: https://npmjs.com/package/@kikiutils/node
+[npm-version-src]: https://img.shields.io/npm/v/@kikiutils/node/latest.svg?style=flat&colorA=18181B&colorB=28CF8D
 
-[npm-downloads-src]: https://img.shields.io/npm/dm/@kikiutils/node.svg?style=flat&colorA=18181B&colorB=28CF8D
 [npm-downloads-href]: https://npmjs.com/package/@kikiutils/node
+[npm-downloads-src]: https://img.shields.io/npm/dm/@kikiutils/node.svg?style=flat&colorA=18181B&colorB=28CF8D
+
+[codecov-href]: https://codecov.io/github/kiki-kanri/kikiutils-node
+[codecov-src]: https://codecov.io/github/kiki-kanri/kikiutils-node/graph/badge.svg?token=GRSQ7JO39E
 
-[license-src]: https://img.shields.io/npm/l/@kikiutils/node.svg?style=flat&colorA=18181B&colorB=28CF8D
 [license-href]: https://github.com/kiki-kanri/kikiutils-node/blob/main/LICENSE
+[license-src]: https://img.shields.io/npm/l/@kikiutils/node.svg?style=flat&colorA=18181B&colorB=28CF8D