docs: Add dependency on sphinx_design.

Adds a dependency on "sphinx_design" for the docs system.  Allows
supporting tabs inside the developer documentatoin.  This is a
preparation commit for later refactoring of the OS-specific setup
documentation.

docs/conf.py

@@ -2,6 +2,7 @@
 # https://www.sphinx-doc.org/en/master/usage/configuration.html
 # https://myst-parser.readthedocs.io/en/latest/sphinx/reference.html
 # https://sphinx-rtd-theme.readthedocs.io/en/stable/configuring.html
+# https://sphinx-design.readthedocs.io/en/latest/tabs.html
 
 import os
 import sys
@@ -17,6 +18,7 @@ on_rtd = os.environ.get("READTHEDOCS") == "True"
 extensions = [
     "myst_parser",
     "sphinx_rtd_theme",
+    "sphinx_design",
 ]
 templates_path = ["_templates"]
 project = "Zulip"

requirements/dev.txt

@@ -2809,8 +2809,13 @@ sphinx==7.1.2 \
     # via
     #   -r requirements/docs.in
     #   myst-parser
+    #   sphinx-design
     #   sphinx-rtd-theme
     #   sphinxcontrib-jquery
+sphinx-design==0.5.0 \
+    --hash=sha256:1af1267b4cea2eedd6724614f19dcc88fe2e15aff65d06b2f6252cee9c4f4c1e \
+    --hash=sha256:e8e513acea6f92d15c6de3b34e954458f245b8e761b45b63950f65373352ab00
+    # via -r requirements/docs.in
 sphinx-rtd-theme==2.0.0 \
     --hash=sha256:bd5d7b80622406762073a04ef8fadc5f9151261563d47027de09910ce03afe6b \
     --hash=sha256:ec93d0856dc280cf3aee9a4c9807c60e027c7f7b461b77aeffed682e68f0e586

requirements/docs.in

@@ -10,6 +10,7 @@
 # Needed to build RTD docs
 sphinx
 sphinx-rtd-theme
+sphinx-design
 
 # Needed to build Markdown docs
 MyST-Parser

requirements/docs.txt

@@ -295,8 +295,13 @@ sphinx==7.1.2 \
     # via
     #   -r requirements/docs.in
     #   myst-parser
+    #   sphinx-design
     #   sphinx-rtd-theme
     #   sphinxcontrib-jquery
+sphinx-design==0.5.0 \
+    --hash=sha256:1af1267b4cea2eedd6724614f19dcc88fe2e15aff65d06b2f6252cee9c4f4c1e \
+    --hash=sha256:e8e513acea6f92d15c6de3b34e954458f245b8e761b45b63950f65373352ab00
+    # via -r requirements/docs.in
 sphinx-rtd-theme==2.0.0 \
     --hash=sha256:bd5d7b80622406762073a04ef8fadc5f9151261563d47027de09910ce03afe6b \
     --hash=sha256:ec93d0856dc280cf3aee9a4c9807c60e027c7f7b461b77aeffed682e68f0e586