DOC: Add Zulip announcement banner and mention in docs (#11246)

Co-authored-by: Ian Hunt-Isaak <ianhuntisaak@gmail.com>

Author: VeckoTheGecko

CORE_TEAM_GUIDE.md

@@ -272,6 +272,7 @@ resources such as:
 - [`pre-commit`](https://pre-commit.com) hooks for autoformatting.
 - [`ruff`](https://github.com/astral-sh/ruff) autoformatting and linting.
 - [python-xarray](https://stackoverflow.com/questions/tagged/python-xarray) on Stack Overflow.
+- The Xarray channel in the [OSSci Zulip](https://ossci.zulipchat.com/)
 - [@xarray_dev](https://x.com/xarray_dev) on X.
 - [xarray-dev](https://discord.gg/bsSGdwBn) discord community (normally only used for remote synchronous chat during sprints).
 

doc/conf.py

@@ -233,6 +233,7 @@
     "header_links_before_dropdown": 8,
     "navbar_align": "left",
     "footer_center":["last-updated"],
+    "announcement": "Xarray now has a home in the <a href='https://ossci.zulipchat.com/'>OSSci Zulip</a>! Chat here with other devs, users, and our friends at Zarr.", # TODO: Remove a couple months'ish after 21 March 2026
     # Instead of adding these to the header bar they are linked in 'getting help' and 'contributing'
     # "icon_links": [
     # {

doc/contribute/contributing.rst

@@ -18,8 +18,8 @@ All contributions, including bug reports, bug fixes, documentation improvements,
 and other ideas are welcome.
 
 If you have any questions on the process or how to fix something feel free to ask us!
-The recommended place to ask a question is  on `GitHub Discussions <https://github.com/pydata/xarray/discussions>`_
-, but we also have a `Discord <https://discord.com/invite/wEKPCt4PDu>`_ and a
+The recommended places to ask questions are `GitHub Discussions <https://github.com/pydata/xarray/discussions>`_
+or the Xarray channel in the `OSSci Zulip <https://ossci.zulipchat.com/#narrow/channel/582428-Xarray>`_. We also have a `Discord <https://discord.com/invite/wEKPCt4PDu>`_ and a
 `mailing list <https://groups.google.com/g/xarray>`_. There is also a
 `"python-xarray" tag on Stack Overflow <https://stackoverflow.com/questions/tagged/python-xarray>`_ which we monitor for questions.