doc: Document the switch from Slack to Discord

After the Technical Steering Committee decided to approve the transition
from Slack to Discord, it is necessary to update all the documentation
to reflect this change.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>

Author: carlescufi

README.rst

@@ -39,7 +39,7 @@ and the documentation's `Getting Started Guide`_ to start developing.
 Community Support
 *****************
 
-Community support is provided via mailing lists and Slack; see the Resources
+Community support is provided via mailing lists and Discord; see the Resources
 below for details.
 
 .. _project-resources:
@@ -64,8 +64,8 @@ Here's a quick summary of resources to help you find your way around:
 * **Nightly CI Build Status**: https://lists.zephyrproject.org/g/builds
   The builds@lists.zephyrproject.org mailing list archives the CI
   (buildkite) nightly build results.
-* **Chat**: Zephyr's Slack workspace is https://zephyrproject.slack.com.  Use
-  this `Slack Invite`_ to register.
+* **Chat**: Real-time chat happens in Zephyr's Discord Server. Use
+  this `Discord Invite`_ to register.
 * **Contributing**: see the `Contribution Guide`_
 * **Wiki**: `Zephyr GitHub wiki`_
 * **Issues**: https://github.com/zephyrproject-rtos/zephyr/issues
@@ -74,7 +74,7 @@ Here's a quick summary of resources to help you find your way around:
   tracked separately at https://zephyrprojectsec.atlassian.net.
 * **Zephyr Project Website**: https://zephyrproject.org
 
-.. _Slack Invite: https://tinyurl.com/2vue8666
+.. _Discord Invite: https://chat.zephyrproject.org
 .. _supported boards: http://docs.zephyrproject.org/latest/boards/index.html
 .. _Zephyr Documentation: http://docs.zephyrproject.org
 .. _Introduction to Zephyr: http://docs.zephyrproject.org/latest/introduction/index.html

doc/contribute/index.rst

@@ -205,15 +205,16 @@ Pull Requests and Issues
 
 .. _Zephyr devel mailing list: https://lists.zephyrproject.org/g/devel
 
-.. _Zephyr Slack channel: https://zephyrproject.slack.com
+.. _Zephyr Discord Server: https://chat.zephyrproject.org
 
 Before starting on a patch, first check in our issues `Zephyr Project Issues`_
 system to see what's been reported on the issue you'd like to address.  Have a
-conversation on the `Zephyr devel mailing list`_ (or the the `Zephyr Slack channel`_)
-to see what others think of your issue (and proposed solution).  You may find
-others that have encountered the issue you're finding, or that have similar
-ideas for changes or additions.  Send a message to the `Zephyr devel mailing list`_
-to introduce and discuss your idea with the development community.
+conversation on the `Zephyr devel mailing list`_ (or the the `Zephyr Discord
+Server`_) to see what others think of your issue (and proposed solution).  You
+may find others that have encountered the issue you're finding, or that have
+similar ideas for changes or additions.  Send a message to the `Zephyr devel
+mailing list`_ to introduce and discuss your idea with the development
+community.
 
 It's always a good practice to search for existing or related issues before
 submitting your own. When you submit an issue (bug or feature request), the

doc/getting_started/index.rst

@@ -623,13 +623,12 @@ Here are some next steps for exploring Zephyr:
 Asking for Help
 ***************
 
-You can ask for help on a mailing list or on Slack. Please send bug reports and
+You can ask for help on a mailing list or on Discord. Please send bug reports and
 feature requests to GitHub.
 
 * **Mailing Lists**: users@lists.zephyrproject.org is usually the right list to
   ask for help. `Search archives and sign up here`_.
-* **Slack**: Zephyr's workspace is https://zephyrproject.slack.com; you can
-  register with this `Slack invite`_.
+* **Discord**: You can join with this `Discord invite`_.
 * **GitHub**: Use `GitHub issues`_ for bugs and feature requests.
 
 How to Ask
@@ -656,9 +655,9 @@ Text includes source code, terminal commands, and their output.
 Doing this makes it easier for people to help you, and also helps other users
 search the archives.
 
-When copy/pasting more than 5 lines of text into Slack, create a `snippet`_.
+When copy/pasting more than 5 lines of text into Discord, create a snippet using
+three backticks to delimit the snippet.
 
 .. _Search archives and sign up here: https://lists.zephyrproject.org/g/users
-.. _Slack invite: https://tinyurl.com/2vue8666
+.. _Discord invite: https://chat.zephyrproject.org
 .. _GitHub issues: https://github.com/zephyrproject-rtos/zephyr/issues
-.. _snippet: https://get.slack.help/hc/en-us/articles/204145658-Create-a-snippet