Include docs in release archives

Author: tarleb

Makefile

@@ -29,10 +29,19 @@ docker-test-image: .tools/Dockerfile
 .PHONY: collection
 collection: .build/lua-filters
 
-.build/lua-filters: $(FILTER_FILES) CONTRIBUTING.md LICENSE README.md
-	mkdir -p .build/lua-filters
-	cp -a $(FILTER_FILES) .build/lua-filters
-	cp -a CONTRIBUTING.md LICENSE README.md .build/lua-filters
+.PHONY: docs
+docs:
+
+.build/lua-filters: $(FILTER_FILES) docs \
+		CONTRIBUTING.md LICENSE README.md
+	mkdir -p $@
+	mkdir -p $@/filters
+	mkdir -p $@/docs
+	cp -a CONTRIBUTING.md LICENSE README.md $@
+	cp -a $(FILTER_FILES) $@/filters
+	for filter in $(FILTERS); do \
+	    cp $$filter/README.md $@/docs/$$filter.md; \
+	done
 	@printf "Filters collected in '%s'\n" "$@"
 
 .build/lua-filters.tar.gz: .build/lua-filters