Moved README links to links.md(#250)

Author: Theo Geddes

README.md

@@ -1,8 +1,8 @@
 # ESMValTool Tutorial
 
 [![Join the chat at
-https://gitter.im/ESMValGroup/Tutorial](https://badges.gitter.im/ESMValGroup/Tutorial.svg)](https://gitter.im/ESMValGroup/Tutorial?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.3974592.svg)](https://doi.org/10.5281/zenodo.3974592)
+https://gitter.im/ESMValGroup/Tutorial][gitter-badge]][gitter]
+[![DOI][zenodo-badge]][zenodo]
 
 
 [ESMValTool Tutorial][tutorial-site] is an open-source project in

_includes/links.md

@@ -16,6 +16,8 @@
 [ds]: https://github.com/ESMValGroup/ESMValTool_Tutorial/blob/main/data/dataset.urls
 [email]: mailto:[email protected]
 [github-importer]: https://import.github.com/
+[gitter-badge]: https://badges.gitter.im/ESMValGroup/Tutorial.svg
+[gitter]: https://gitter.im/ESMValGroup/Tutorial?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
 [importer]: https://github.com/new/import
 [install-from-source]: https://docs.esmvaltool.org/en/latest/quickstart/installation.html#install-from-source
 [interface]: https://docs.esmvaltool.org/projects/esmvalcore/en/latest/interfaces.html
@@ -59,3 +61,5 @@
 [training]: https://carpentries.github.io/instructor-training/
 [workshop-repo]: {{ site.workshop_repo }}
 [yaml]: http://yaml.org/
+[zenodo-badge]: https://zenodo.org/badge/DOI/10.5281/zenodo.3974592.svg
+[zenodo]: https://doi.org/10.5281/zenodo.3974592