Added example of docker invocation to the Makefile

As suggested by @leoheck in 2233c0e08a

Makefile

@@ -3,6 +3,10 @@ tagname = 10.4-5.1.6
 docker_user = setsoft
 docker_img = setsoft/kicad_auto
 
+CWD := $(abspath $(patsubst %/,%,$(dir $(abspath $(lastword $(MAKEFILE_LIST))))))
+USER_ID=$(shell id -u)
+GROUP_ID=$(shell id -g)
+
 download_packages:
 	./download.sh
 
@@ -17,7 +21,7 @@ upload_image:
 
 release: build upload_image
 
-# If docker is not installer int the host system
+# If docker is not installed in the host system
 install_docker:
 	sudo apt install docker.io
 	sudo systemctl enable --now docker
@@ -26,5 +30,18 @@ install_docker:
 clean:
 	@ rm -rf *.deb
 
+# Docker shell for the current user.
+# You can access the desktop and your home.
+# Changes to the docker image are discarded, but changes to your home are real changes.
+docker_shell:
+	docker run  -it --rm -v $(CWD):$(CWD) --workdir="$(CWD)" \
+	-v /tmp/.X11-unix:/tmp/.X11-unix -e DISPLAY=$(DISPLAY) \
+	--user $(USER_ID):$(GROUP_ID) \
+	--volume="/etc/group:/etc/group:ro" \
+	--volume="/etc/passwd:/etc/passwd:ro" \
+	--volume="/etc/shadow:/etc/shadow:ro" \
+	--volume="/home/$(USER):/home/$(USER):rw" \
+	$(docker_img):$(tagname) /bin/bash
+
 .PHONY: download_packages build_release upload_image install_docker clean