feat: support cd - (cd last)

[leyiang]

Support cd -, go to last visit dir.
I konw in #1913 you metioned there's back and forward, but it's logic is not exactly the same with cd -, "back" shift from backstack but won't add current cwd into it.

yazi/yazi-config/preset/keymap.toml

Lines 42 to 43 in af565fb

	{ on = "H", run = "back", desc = "Go back to the previous directory" },
	{ on = "L", run = "forward", desc = "Go forward to the next directory" },

cd - can toggle between two places, I know we can simulate this with tabs. But I personally want the cd - feature, feel free to close or merge this PR.

[sxyazi]

Please create a new dedicated command called flip for it, because cd is not just a command, but also an important API that will be used in the plugin system.

Supporting cd - would affect cases where the directory name itself is - (I know this might not be very common, but I want to keep the behavior of cd as consistent as possible).