I use markdown extension on chrome to see md files written in vim - if I have to !  

As for writing docs .. #mdbook is my go to .. with mdbook I can serve the book to localhost which is pretty nice to review the work .. 

On vim plug-ins .. my fav is coc-vim .. it has everything - spell checkers  and language tool for grammar ..  and most of the code analyzers too ..just in case you wanna review code ..

But the primary reason , I stick to vim is it is great  in terminal .. firing up GUI on my old desktop makes it super sluggish :-)  And my laptop always stays in back pack :-)