fix markdown syntax for vim (autozimu#1155)

Author: rottencandy

autoload/LanguageClient.vim

@@ -551,6 +551,8 @@ function! s:OpenHoverPreview(bufname, lines, filetype, ...) abort
  let pop_win_id = popup_atcursor(a:lines, { 'padding': l:padding })
  endif
  call setbufvar(winbufnr(pop_win_id), '&filetype', a:filetype)
+ " trigger refresh on plasticboy/vim-markdown
+ call win_execute(pop_win_id, 'doautocmd InsertLeave')
  elseif display_approach ==# 'preview'
  execute 'silent! noswapfile pedit!' a:bufname
  wincmd P