Add NexTool to Developer Tools section

Author: Christian B

README.md

@@ -308,6 +308,7 @@
 - [snippet generator](https://snippet-generator.app/)
 - [Front-End Checklist](https://frontendchecklist.io/)
 - [BundlePhobia](https://bundlephobia.com/) - Cost of adding an npm package
+- [NexTool](https://nextool.app/free-tools/) - 228+ free browser-based developer tools. JSON, CSS, regex, images, encoding, hashing, and more. No signup.
 - [iHateRegex](https://ihateregex.io/) - Regex Cheat Sheet
 - [RegExr](https://regexr.com/) - Learn, Build, & Test RegEx
 - [regular expressions 101](https://regex101.com/) - Build, Debug, & Share regex