feat: copy/paste to system clipboard

[stevalkr]

This PR implements basic features of

• feature request: copy/paste to system clipboard #556
• feature request: pasting path of files into an oil buffer #156

[stevalkr]

Hi @stevearc, I’m having a bit of trouble with the sshFs.load function. It works great for SSH connections that don’t require passwords, but for those that do, the float window can’t open because vim.wait is blocking it. Is there a way to let this function wait for the connection without blocking vim.api.nvim_open_win?

[stevalkr]

This modification allows inputting passwords during vim.wait. However, without implementing additional logic to detect incorrect passwords (Permission denied), the behavior will be weird if the password is incorrect.