Makefile: Fix .min.css filename and include headless variant in assets

Also include the unminified versions for people who wants to modify
them.

Makefile

@@ -100,10 +100,14 @@ release:
 	make po2json
 	make build
 	mkdir -p 'converse-assets-$(VERSION)'
+	$(INSTALL) -D dist/converse.js 'converse-assets-$(VERSION)/converse.js'
 	$(INSTALL) -D dist/converse.min.js 'converse-assets-$(VERSION)/converse.min.js'
 	$(INSTALL) -D dist/converse.min.js.map 'converse-assets-$(VERSION)/converse.min.js.map'
-	$(INSTALL) -D css/converse.min.css \
-		'converse-assets-$(VERSION)/css/converse.css'
+	$(INSTALL) -D dist/converse-headless.js 'converse-assets-$(VERSION)/converse-headless.js'
+	$(INSTALL) -D dist/converse-headless.min.js 'converse-assets-$(VERSION)/converse-headless.min.js'
+	$(INSTALL) -D dist/converse-headless.min.js.map 'converse-assets-$(VERSION)/converse-headless.min.js.map'
+	$(INSTALL) -D css/converse.css 'converse-assets-$(VERSION)/css/converse.css'
+	$(INSTALL) -D css/converse.min.css 'converse-assets-$(VERSION)/css/converse.min.css'
 	cp -r css/webfonts 'converse-assets-$(VERSION)/css/'
 	cp -r sounds 'converse-assets-$(VERSION)/'
 	find locale -type f -name '*.json' \
@@ -125,7 +129,7 @@ stamp-npm: $(LERNA) package.json package-lock.json src/headless/package.json
 .PHONY: clean
 clean:
 	rm -rf node_modules stamp-npm
-	rm -f dist/*.min.js
+	rm -f dist/*.min.js*
 	rm -f css/*.min.css
 	rm -f css/*.map
 	rm -f css/*.zip