Adds help command

Adds help command in make file.

makefile

@@ -10,20 +10,20 @@ html2:
 	# cp -fvr images _book/
 	cp -fvr _main* _book/
 
-build:
+build: ## Make Build
 	make html
 	Rscript -e 'browseURL("_book/index.html")'
 
-pdf:
+pdf: ## Render book in pdf
 	Rscript -e 'bookdown::render_book("index.Rmd", output_format = "bookdown::pdf_book")'
 
-md:
+md: ## Generate Markdown
 	Rscript -e 'bookdown::render_book("index.Rmd", output_format = "bookdown::pdf_book", clean = FALSE)'
 
-install:
+install: ## Perform install
 	Rscript -e 'remotes::install_github("Robinlovelace/geocompr")'
 
-deploy:
+deploy: ## Perform deployment
 	Rscript -e 'bookdown::publish_book(render = "local", account = "robinlovelace")'
 
 clean:
@@ -36,3 +36,7 @@ cleaner:
 	rm -fvr *.html # rogue html files
 	rm -fvr *utf8.md # rogue md files
 
+.PHONY: help
+help: SHELL := /bin/sh
+help: ## List available commands and their usage
+	@awk 'BEGIN {FS = ":.*?##"; printf "\nUsage:\n  make \033[36m<target>\033[0m\n\nTargets:\n"} /^[0-9a-zA-Z_-]+:.*?##/ { printf "  \033[36m%-20s\033[0m %s\n", $$1, $$2 } ' $(MAKEFILE_LIST)