[readme] update badges

readme.markdown

@@ -1,15 +1,13 @@
-# object-inspect <sup>[![Version Badge][2]][1]</sup>
+# object-inspect <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
 
 string representations of objects in node and the browser
 
 [![github actions][actions-image]][actions-url]
 [![coverage][codecov-image]][codecov-url]
-[![dependency status][5]][6]
-[![dev dependency status][7]][8]
 [![License][license-image]][license-url]
 [![Downloads][downloads-image]][downloads-url]
 
-[![npm badge][11]][1]
+[![npm badge][npm-badge-png]][package-url]
 
 # example
 
@@ -69,13 +67,13 @@ npm install object-inspect
 
 MIT
 
-[1]: https://npmjs.org/package/object-inspect
-[2]: https://versionbadg.es/inspect-js/object-inspect.svg
-[5]: https://david-dm.org/inspect-js/object-inspect.svg
-[6]: https://david-dm.org/inspect-js/object-inspect
-[7]: https://david-dm.org/inspect-js/object-inspect/dev-status.svg
-[8]: https://david-dm.org/inspect-js/object-inspect#info=devDependencies
-[11]: https://nodei.co/npm/object-inspect.png?downloads=true&stars=true
+[package-url]: https://npmjs.org/package/object-inspect
+[npm-version-svg]: https://versionbadg.es/inspect-js/object-inspect.svg
+[deps-svg]: https://david-dm.org/inspect-js/object-inspect.svg
+[deps-url]: https://david-dm.org/inspect-js/object-inspect
+[dev-deps-svg]: https://david-dm.org/inspect-js/object-inspect/dev-status.svg
+[dev-deps-url]: https://david-dm.org/inspect-js/object-inspect#info=devDependencies
+[npm-badge-png]: https://nodei.co/npm/object-inspect.png?downloads=true&stars=true
 [license-image]: https://img.shields.io/npm/l/object-inspect.svg
 [license-url]: LICENSE
 [downloads-image]: https://img.shields.io/npm/dm/object-inspect.svg