Add <plug>(plug-preview) map

[junegunn]

This allows you to override the default behavior of o or <cr> binding in PlugDiff window.

" Move to preview window
autocmd! FileType vim-plug nmap <buffer> o <plug>(plug-preview)<c-w>P

Close #749
Close #768

[cbcoutinho]

How do you use this? Do I need to include it in my vimrc or is it in the latest master of plug-vim?

[nfischer]

@cbcoutinho run :PlugUpgrade to get the latest version of vim-plug, then add the vimscript in #769 (comment) into your vimrc (the default behavior is the same, this vimscript configures it). Restart vim and try it out 😄

@junegunn this is great!