Add deadcode linter step in makefile

Author: arbulu89

Makefile

@@ -96,3 +96,16 @@ test-coverage:
 .PHONY: test-build
 test-build:
 	bats -r ./test
+
+.PHONY: deadcode
+deadcode:
+ifeq (, $(shell command -v deadcode 2> /dev/null))
+	$(error "'deadcode' command not found. You can install it locally with 'go install golang.org/x/tools/cmd/deadcode@latest'.")
+endif
+	@out=$$(deadcode -test ./... 2>/dev/null); \
+	if [ -n "$$out" ] && [ "$$out" != "null" ]; then \
+		echo "Dead code detected:" >&2; \
+		echo "$$out" >&2; \
+		exit 1; \
+	fi
+	@echo "No dead code found."