docs: improve makefile documentation and add usage help target

- Add comments to describe various make targets such as `build`, `install`, `test`, and different platform-specific builds.
- Add a `help` target to print usage information for the makefile.

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

Author: appleboy

Makefile

@@ -17,28 +17,42 @@ else
 endif
 COMMIT ?= $(shell git rev-parse --short HEAD)
 
+## build: build the codegpt binary
 build: $(EXECUTABLE)
 
 $(EXECUTABLE): $(GOFILES)
 	$(GO) build -v -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o bin/$@ ./cmd/$(EXECUTABLE)
 
+## install: install the codegpt binary
 install: $(GOFILES)
 	$(GO) install -v -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)'
 
+## test: run tests
 test:
 	@$(GO) test -v -cover -coverprofile coverage.txt ./... && echo "\n==>\033[32m Ok\033[m\n" || exit 1
 
+## build_linux_amd64: build the codegpt binary for linux amd64
 build_linux_amd64:
 	CGO_ENABLED=0 GOOS=linux GOARCH=amd64 $(GO) build -a -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o release/linux/amd64/$(EXECUTABLE) ./cmd/$(EXECUTABLE)
 
+## build_linux_arm64: build the codegpt binary for linux arm64
 build_linux_arm64:
 	CGO_ENABLED=0 GOOS=linux GOARCH=arm64 $(GO) build -a -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o release/linux/arm64/$(EXECUTABLE) ./cmd/$(EXECUTABLE)
 
+## build_linux_arm: build the codegpt binary for linux arm
 build_linux_arm:
 	CGO_ENABLED=0 GOOS=linux GOARCH=arm GOARM=7 $(GO) build -a -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o release/linux/arm/$(EXECUTABLE) ./cmd/$(EXECUTABLE)
 
+## build_mac_intel: build the codegpt binary for mac intel
 build_mac_intel:
 	CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 $(GO) build -a -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o release/mac/intel/$(EXECUTABLE) ./cmd/$(EXECUTABLE)
 
+## build_windows_64: build the codegpt binary for windows 64
 build_windows_64:
 	CGO_ENABLED=0 GOOS=windows GOARCH=amd64 $(GO) build -a -tags '$(TAGS)' -ldflags '$(EXTLDFLAGS)-s -w $(LDFLAGS)' -o release/windows/intel/$(EXECUTABLE).exe ./cmd/$(EXECUTABLE)
+
+## help: print this help message
+.PHONY: help
+help:
+	@echo 'Usage:'
+	@sed -n 's/^##//p' ${MAKEFILE_LIST} | column -t -s ':' | sed -e 's/^/ /'