System: MacOS Mojave. Other OS can refer to this as well, as long as the Vim command is changed accordingly.

Download a Chrome extension called Markdown preview.

Download this extension and check “Allow access to file URLs” in chrome://extensions listing.

Map a key in Vim to pen the file with Chrome

I map <F5> to a command that saves the current file and open it in Chrome:

autocmd BufEnter *.md exe 'noremap <F5> :w <bar> silent ! /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome %:p<CR>' 

Reference: https://stackoverflow.com/questions/9212340/is-there-a-vim-plugin-for-previewing-markdown-files