Add README.md and Makefile.

Makefile

@@ -0,0 +1,35 @@
+SHELL := /usr/local/bin/oksh
+export PATH := $(PATH)
+
+all: fmt lintfix test clean build
+
+clean:
+	rm ./main
+
+debug:
+	@echo "PATH: $(PATH)"
+	@echo "GOPATH: $(shell go env GOPATH)"
+	@which go
+	@which gofumpt
+	@which gci
+	@which golangci-lint
+
+# Test
+test:
+	go test ./...
+
+# Format code
+fmt:
+	gofumpt -l -w .
+	gci write .
+
+# Run linter
+lint: fmt
+	golangci-lint run
+
+# Run linter and fix
+lintfix: fmt
+	golangci-lint run --fix
+
+build:
+	go build ./main.go