docs: add hardware recommendation

Also add infrastructure to also generate the supported hardware
page when building the docs locally

doc/Makefile

@@ -12,9 +12,13 @@ BUILDDIR      = _build
 help:
 	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
 
+hardware.rst: hardware.nix
+	@rm -f hardware.rst || true
+	@cp $$(nix-build hardware.nix) hardware.rst
+
 .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 $(SPHINXOPTS).
-%: Makefile
+html: Makefile
 	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)