Modernize docs/Makefile with help from sphinx-quickstart (PlasmaP…

…y#2463)

* Update docs/Makefile

* Update docs/Makefile

* Add back some make recipes

* Update .gitignore

* Make comment timeless

Words like "new" become obsolete over time

.gitignore

@@ -149,3 +149,4 @@ untitled*
 .mypy_cache
 node_modules
 package-lock.json
+monkeytype.sqlite3

docs/Makefile

@@ -1,32 +1,27 @@
 # Minimal makefile for Sphinx documentation
-#
 
-# You can set these variables from the command line.
-SPHINXOPTS    =
-SPHINXBUILD   = python -msphinx
-SPHINXPROJ    = plasmapy
-SOURCEDIR     = .
-BUILDDIR      = _build
+# 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)
-
-clean:
-	rm -rf $(BUILDDIR)/*
-	rm -rf api cache gen_modules __pycache
-
 clean-api:
 	rm -rf api
 
 html-nonb: Makefile
 	@echo $(SPHINXBUILD) -M html "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) -D nbsphinx_execute='never' $(O)
 	@$(SPHINXBUILD) -M html "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) -D nbsphinx_execute='never' $(O)
 	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html. Jupyter notebooks were skipped."
+
+# Catch-all target: route all unknown targets to Sphinx using the
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)