downgrade sphinx version so that it compiles way faster

Makefile

@@ -56,6 +56,10 @@ clean:
 spelling:
 	$(SPHINXBUILD) -b spelling . _spelling
 
+.PHONY: fast-html
+fast-html:
+	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(EXTENSIONS) $(BUILDDIR)
+
 .PHONY: html
 html:
 	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(EXTENSIONS) $(BUILDDIR)
@@ -141,15 +145,6 @@ qthelp:
 	@echo "To view the help file:"
 	@echo "# assistant -collectionFile $(BUILDDIR)/qthelp/textbook.qhc"
 
-.PHONY: applehelp
-applehelp:
-	$(SPHINXBUILD) -b applehelp $(ALLSPHINXOPTS) $(BUILDDIR)/applehelp
-	@echo
-	@echo "Build finished. The help book is in $(BUILDDIR)/applehelp."
-	@echo "N.B. You won't be able to view it unless you put it in" \
-	      "~/Library/Documentation/Help or install it in your application" \
-	      "bundle."
-
 .PHONY: devhelp
 devhelp:
 	$(SPHINXBUILD) -b devhelp $(ALLSPHINXOPTS) $(BUILDDIR)/devhelp

index.rst

@@ -6,7 +6,6 @@ by :ref:`Dr. Marc Lichtman<author-chapter>` - [email protected]
 
 Welcome to PySDR, a free online textbook that provides a gentle introduction to wireless communications and software-defined radio (SDR) using an abundance of diagrams, animations, and Python code examples. The primary goal of PySDR is to increase accessibility to topics traditionally covered at the graduate level within a relatively small set of universities. All content of PySDR is open source, even the code used to generate the figures/animations, and can be found `here <https://github.com/777arc/PySDR>`_.
 
-
 See Chapter 1: :ref:`intro-chapter` for the textbook's purpose and target audience.
 
 .. raw:: html

requirements.txt

@@ -1,6 +1,12 @@
-sphinx==7.3.7
+sphinx==4.4.0
 sphinxcontrib-tikz==0.4.20
 sphinxcontrib-spelling==8.0.0
-docutils==0.21.2
+docutils==0.17.1
 patreon==0.5.0
 imageio==2.11.0
+sphinxcontrib-applehelp==1.0.2
+sphinxcontrib-devhelp==1.0.2
+sphinxcontrib-htmlhelp==2.0.0
+sphinxcontrib-jsmath==1.0.1
+sphinxcontrib-qthelp==1.0.3
+sphinxcontrib-serializinghtml==1.1.5