Detect broken socket and reconnect automatically

[mbostock]

If the socket closes, the client never tries to reopen and reconnect.

[mbostock]

We could also do a version check and reload the page (avoiding the client running stale code during development).

[code-SL]

Note that in neovim, set backupcopy=yes needs to be set or else socket is closed upon save. Emacs doesn't seem to exhibit the same problematic default setting that closes upon save.

[Fil]

related #563

[eitanlees]

Thank you @code-SL for the neovim solution!

I added the following to ~/.config/nvim/init.lua

vim.opt.backupcopy = 'yes'

and that alleviated the issue.