Make help.md

I prefer a help rule in the Makefile, like so:

   help:
        @grep -P '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-20s\033[0m %s\n", $$1, $$2}'
Assuming that the trimmed Makefile read:

   build: ## Build the binary

   clean: ## Clean the binary and intermediate files

   distclean: clean ## Clean dependencies, intermediate files and binary

   deps: ## Install dependencies

   all: deps build ## Get dependencies and build binary

   release: distclean all ## distclean + all