Add new example as per the tutorial

examples/stm32/stm32-nucleo-f746zg/Makefile

@@ -0,0 +1,18 @@
+NAME ?= $(notdir $(CURDIR))
+
+$(NAME):
+	git clone --depth 1 https://github.com/mongoose-examples/$(NAME)
+
+build: | $(NAME)
+	cp ./../../../mongoose.c $(NAME)/Core/Src/
+	cp ./../../../mongoose.h $(NAME)/Core/Inc/
+	make -C $(NAME) build
+
+clean:
+	rm -rf $(NAME)
+
+flash:
+	make -C $(NAME) flash
+
+.PHONY: flash
+