Docs: Use Sphinx for the documentation (#80)

We're saying goodbye to MkDocs and switching over to Sphinx! This allows
us to use intersphinx with the Python docs, and also allows us to have a
nice reference documentation.

Author: ZeroIntensity

.gitignore

@@ -10,6 +10,8 @@ dist/
 src/pyawaitable/pyawaitable.h
 pcbuild/
 *.o
+site/
+_build/
 
 # LSP
 compile_flags.txt

docs/Makefile

@@ -0,0 +1,20 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = .
+BUILDDIR      = _build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)