Support lcd and tcd for switching directory

[Kailian-Jacy]

Some may wants to edit multiple projects simultaneously in multiple nvim windows which belongs to different paths. And we need to set different working directory separately for each of the windows.

Nvim provides multiple cd-variants for similar demands.

It seems current cd-project only hard code cd that modifies global working directory of the top level.

Adding an optional parameter in the current api should be easy and safe.

I suggest:

• Exposing an optional param in api.cd_project to switch different cds.
• Suggest users with lcd needs to bind another keymaps like <leader>fP = CdProject(cd = "lcd")