Add Vim markdown config plugin

if !exists('g:markdown_fenced_languages')

	let g:markdown_fenced_languages = []

endif

let g:markdown_fenced_languages += ['python', 'bash=sh', 'go', 'c', 'make']

let g:markdown_fenced_languages += ['nginx', 'html', 'css', 'less', 'javascript']

let g:markdown_fenced_languages += ['json', 'yaml', 'xml']