Merge pull request #867 from XinShen-CHN/Add-slack-channel-to-"Where-…

…can-I-find-help"-#838

Add the slack channel.

docs/source/userguide/beginners_guide.rst

@@ -16,7 +16,7 @@ FESTIM is under version control with `git <https://git-scm.com/>`_. Even though
 Where can I find help?
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-If you're having an issue, the best way to find help is to join the `FESTIM discourse <https://festim.discourse.group>`_. Engage in discussions, ask questions, and connect with other users. This collaborative space allows you to share your experiences and seek assistance.
+If you're having an issue, the best way to find help is to join the `FESTIM discourse <https://festim.discourse.group>`_. Engage in discussions, ask questions, and connect with other users. This collaborative space allows you to share your experiences and seek assistance. `Slack <https://join.slack.com/t/festim-dev/shared_invite/zt-246hw8d6o-htWASLsbdosUo_2nRKCf9g>`_ is also a good place to discuss.
 
 
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