Support pinning working directory on per buffer or per window basis

[rameshsanth]

This PR allows user to set the working directory and project.nvim will remember the setting.
This is useful when browsing large projects.

Per buffer: enable_buffer_local_dir

• the buffer with different directory will always open in that directory.

Per window: enable_window_local_dir

• all files opened in that window will be have the directory that it was set.

[atlas-comstock]

This is quite helpful , can @ahmedkhalf help to review and merge it?

[atlas-comstock]

I started using this MR in my env, works pretty well, thanks

[rameshsanth]

@ahmedkhalf Ahmed, if you're busy, can you add someone else who has time to review and merge the PR's. Don't turn this project into abandonware.

[9mm]

@ahmedkhalf agree, please dont just turn this into abandonware. The PR about overwriting keymaps is also super useful, I"m sure a lot of people would help maintain this