{
	"name": "html",
	"version": "0.1.0",
	"publisher": "vscode",
	"engines": { "vscode": "*" },
	"contributes": {
		"languages": [{
			"id": "html",
			"extensions": [ ".html", ".htm", ".shtml", ".xhtml", ".mdoc", ".jsp", ".asp", ".aspx", ".jshtm" ],
			"aliases": [ "HTML", "htm", "html", "xhtml" ],
			"mimetypes": ["text/html", "text/x-jshtm", "text/template", "text/ng-template"]
		}],
		"grammars": [{
			/* "language": "html", not yet enabled*/
			"scopeName": "text.html.basic",
			"path": "./syntaxes/HTML.plist"
		}]
	}

}
{
	"name": "html",
	"version": "0.1.0",
	"publisher": "vscode",
	"engines": { "vscode": "*" },
	"contributes": {
		"languages": [{
			"id": "html",
			"extensions": [ ".html", ".htm", ".shtml", ".xhtml", ".mdoc", ".jsp", ".asp", ".aspx", ".jshtm" ],
			"aliases": [ "HTML", "htm", "html", "xhtml" ],
			"mimetypes": ["text/html", "text/x-jshtm", "text/template", "text/ng-template", "application/xhtml+xml"]
		}],
		"grammars": [{
			/* "language": "html", not yet enabled*/
			"scopeName": "text.html.basic",
			"path": "./syntaxes/HTML.plist"
		}]
	}

}

Add application/xhtml+xml as a HTML mimetype
Add application/xhtml+xml as a HTML mimetype

Related #3521