[Docs] introduce "make help"

Makefile

@@ -92,6 +92,25 @@ all: build
 
 include docker/Makefile
 
+.PHONY: help
+help:
+	@echo "Make Routines:"
+	@echo " - \"\"                equivalent to \"build\""
+	@echo " - build             creates the entire project"
+	@echo " - clean             delete integration files and build files but not css and js files"
+	@echo " - clean-all         delete all generated files (integration test, build, css and js files)"
+	@echo " - css               rebuild only css files"
+	@echo " - js                rebuild only js files"
+	@echo " - generate          run \"make css js\" and \"go generate\""
+	@echo " - fmt               format the code"
+	@echo " - generate-swagger  generate the swagger spec from code comments"
+	@echo " - swagger-validate  check if the swagger spec is valide"
+	@echo " - revive            run code linter revive"
+	@echo " - misspell          check if a word is written wrong"
+	@echo " - vet               examines Go source code and reports suspicious constructs"
+	@echo " - test              run unit test"
+	@echo " - test-sqlite       run integration test for sqlite"
+
 .PHONY: go-check
 go-check:
 	$(eval GO_VERSION := $(shell printf "%03d%03d%03d" $(shell go version | grep -Eo '[0-9]+\.?[0-9]+?\.?[0-9]?\s' | tr '.' ' ');))