Update Dockerfile and Makefile to support dynamic Hugo version

Dockerfile

@@ -1,4 +1,5 @@
-FROM hugomods/hugo:node
+ARG HUGO_VERSION=
+FROM hugomods/hugo:node-${HUGO_VERSION}
 
 WORKDIR /src
 

Makefile

@@ -26,11 +26,15 @@ check-links-ci: set-up-link-checker run-link-checker
 serve:
 	hugo server --buildDrafts --buildFuture --bind 0.0.0.0
 
+HUGO_VERSION ?= $(shell grep HUGO_VERSION ./netlify.toml | head -1 | cut -d '"' -f 2)
+
+IMAGE_NAME ?= helm-docs
+
 image:
-	docker build -t helm-docs .
+	docker build --build-arg HUGO_VERSION=$(HUGO_VERSION) -t $(IMAGE_NAME) .
 
 # Extract the target after 'image-run' or default to 'serve'
 DOCKER_TARGET = $(if $(filter-out image-run,$(MAKECMDGOALS)),$(filter-out image-run,$(MAKECMDGOALS)),serve)
 
 image-run:
-	docker run --rm --init -it -p 1313:1313 -v $(PWD):/src helm-docs $(DOCKER_TARGET)
+	docker run --rm --init -it -p 1313:1313 -v $(PWD):/src $(IMAGE_NAME) $(DOCKER_TARGET)