Add shellcheck to the deps list

Makefile

@@ -84,6 +84,7 @@ binary-check:
 	$(call checkbin, "rustc", "Install package 'rust'.")
 	$(call checkbin, "cargo", "Install package 'cargo'.")
 	$(call checkbin, "ctags", "Install package 'ctags'.")
+	$(call checkbin, "shellcheck", "Install package 'shellcheck'.")
 	@echo " OK"
 
 prepare: binary-check