Update question Github issue tempate

Update question Github issue template to refer people to Slack channel, and not StackOverflow

.github/ISSUE_TEMPLATE/question.md

@@ -8,7 +8,10 @@ about: If you have a question or run into some problem with Flow (e.g. during th
 PLEASE DO NOT ASK YOUR QUESTIONS HERE ON GITHUB!
 
 If you have a question or run into some problem (e.g. during installation or when running an example)
-with Flow, please direct your technical questions to Stack Overflow using the "flow-project" tag.
+with Flow, please direct technical questions to the Flow project Slack channel here:
 
-link: https://stackoverflow.com/questions/tagged/flow-project
-tag: flow-project
+https://join.slack.com/t/flow-users/shared_invite/enQtODQ0NDYxMTQyNDY2LTY1ZDVjZTljM2U0ODIxNTY5NTQ2MmUxMzYzNzc5NzU4ZTlmNGI2ZjFmNGU4YjVhNzE3NjcwZTBjNzIxYTg5ZmY
+
+If you have a non-technical inquiry, please send us an email:
+
+https://flow-project.github.io/contact.html