add following options to set preview window for hover:
g:LanguageClient_PreviewWindowLoc: the location of PreviewWindow, available is one of: “left”,"right","top","bottom". If setted to invalid value, put it in "top" like the default behavior of vim preview window.
g:LanguageClient_PreviewHeight: the size of PreviewWindow, inspired from vim option "previewheight"
add following options to set preview window for hover: