Add the autosummary generated files to .gitignore and 'make clean' (#363)

Author: asmeurer

.gitignore

@@ -3,4 +3,5 @@ build/
 .vscode/
 node_modules/
 __pycache__/
-*.pyc
+*.pyc
+spec/**/generated

spec/Makefile

@@ -12,9 +12,13 @@ BUILDDIR      = _build
 help:
 	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
 
-.PHONY: help Makefile
+.PHONY: help Makefile clean
 
 # 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 $(BUILDDIR)
+	-rm -rf "$(SOURCEDIR)/API_specification/generated"