'editor.import.extensions' key for setting importable file extensions is available in .

{
    'editor.import.extensions' : ['doc', 'docx', 'hwp', 'hml', 'htm', 'html', 'txt', 'xls', 'xlsx'],
	'editor.upload.image.extensions': ['jpg', 'gif', 'png', 'jpeg'],
	'editor.upload.video.extensions': ['mp4', 'ogg', 'webm'],
	'editor.upload.file.extensions': ['bmp', 'css', 'csv', 'diff', 'doc', 
									'docx', 'eof', 'gif', 'jpeg', 'jpg', 
									'json', 'mp3', 'mp4', 'm4a', 'odp', 
									'ods', 'odt', 'ogg', 'otf', 'patch', 
									'pdf', 'png', 'ppt', 'pptx', 'rtf', 
									'svg', 'swf', 'textile', 'tif', 'tiff',
									'ttf', 'txt', 'wav', 'webm', 'woff',
									'xls', 'xlsx', 'xml', 'md', 'vtt', 
									'hwp', 'hml', 'html']
}