Update README.md

README.md

@@ -95,12 +95,15 @@ url = {https://control-toolbox.org/OptimalControl.jl}
 
 ## Contributing
 
-If you think you found a bug or if you have a feature request or suggestion, feel free to open an [issue](https://github.com/control-toolbox/OptimalControl.jl/issues).
+[issue-url]: https://github.com/control-toolbox/OptimalControl.jl/issues
+[first-good-issue-url]: https://github.com/control-toolbox/OptimalControl.jl/contribute
+
+If you think you found a bug or if you have a feature request or suggestion, feel free to open an [issue][issue-url].
 Before opening a pull request, start an issue or a discussion on the topic, please. 
 
 Any contributions are welcomed, check out [how to contribute to a Github project](https://docs.github.com/en/get-started/exploring-projects-on-github/contributing-to-a-project). 
 If it is your first contribution, you can also check [this first contribution tutorial](https://github.com/firstcontributions/first-contributions).
-You can find first good issues, if any, at the [first good issues page](https://github.com/control-toolbox/OptimalControl.jl/contribute). You may find other packages to contribute to at the [control-toolbox organization](https://github.com/control-toolbox).
+You can find first good issues, if any, at the [first good issues page][first-good-issue-url]. You may find other packages to contribute to at the [control-toolbox organization](https://github.com/control-toolbox).
 
 If you want to ask a question, feel free to start a discussion [here](https://github.com/orgs/control-toolbox/discussions). This forum is for general discussion about this repository and the [control-toolbox organization](https://github.com/control-toolbox), so questions about any of our packages are welcome.