docs: improve build system with enhanced targets and descriptions (#17)

- Add a `help` target to print a help message.
- Add descriptions for the `build`, `air`, `dev`, and `vendor` targets.
- Remove inline comments for the `air`, `dev`, and `vendor` targets.

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/17
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

Makefile

@@ -3,25 +3,30 @@ EXECUTABLE := gitea-mcp
 VERSION ?= $(shell git describe --tags --always | sed 's/-/+/' | sed 's/^v//')
 LDFLAGS := -X "main.Version=$(VERSION)"
 
+.PHONY: help
+help: ## Print this help message.
+	@echo "Usage: make [target]"
+	@echo ""
+	@echo "Targets:"
+	@echo ""
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
+
 .PHONY: build
-build:
+build: ## Build the application.
 	$(GO) build -v -ldflags '-s -w $(LDFLAGS)' -o $(EXECUTABLE)
 
-## air: install air for hot reload
 .PHONY: air
-air:
+air: ## Install air for hot reload.
 	@hash air > /dev/null 2>&1; if [ $$? -ne 0 ]; then \
 		$(GO) install github.com/air-verse/air@latest; \
 	fi
 
-## dev: run the application with hot reload
 .PHONY: dev
-dev: air
+dev: air ## run the application with hot reload
 	air --build.cmd "make build" --build.bin ./gitea-mcp
 
-## vendor: tidy and verify module dependencies
 .PHONY: vendor
-vendor:
+vendor: ## tidy and verify module dependencies
 	@echo 'Tidying and verifying module dependencies...'
 	go mod tidy
-	go mod verify
+	go mod verify