I'm using Grav CMS and this works perfectly:
Body/Content:
Some text[1]
Body/Reference:
[1]: http://somelink.com/?target=_blank
Just make sure that the target attribute is passed first, if there are additional attributes in the link, copy/paste them to the end of the reference URL.
Also work as direct link:
[Go to this page](http://somelink.com/?target=_blank)
grav markdown链接在新窗口打开，链接加target=”_blank”