coredumpctl: add --root= + --image= to --help text

src/coredump/coredumpctl.c

@@ -195,6 +195,8 @@ static int verb_help(int argc, char **argv, void *userdata) {
                "  -D --directory=DIR           Use journal files from directory\n\n"
                "  -q --quiet                   Do not show info messages and privilege warning\n"
                "     --all                     Look at all journal files instead of local ones\n"
+               "     --root=PATH               Operate on an alternate filesystem root\n"
+               "     --image=PATH              Operate on disk image as filesystem root\n"
                "\nSee the %2$s for details.\n",
                program_invocation_short_name,
                link,