Update RELEASE-NOTES.md

Author: OriolAbril

RELEASE-NOTES.md

@@ -129,7 +129,7 @@ This includes API changes we did not warn about since at least `3.11.0` (2021-01
 
 ## Documentation
 - Switched to the [pydata-sphinx-theme](https://pydata-sphinx-theme.readthedocs.io/en/latest/)
-- Updated our documentation tooling to use [MyST](), [MyST-NB](), sphinx-design, notfound.extension,
+- Updated our documentation tooling to use [MyST](https://myst-parser.readthedocs.io/en/latest/), [MyST-NB](https://myst-nb.readthedocs.io/en/latest/), sphinx-design, notfound.extension,
   sphinx-copybutton and sphinx-remove-toctrees.
 - Separated the builds of the example notebooks and of the versioned docs.
 - Restructured the documentation to facilitate learning paths