close #69: add link to demo site

Author: yihui

theme.toml

@@ -3,6 +3,7 @@ license = "MIT"
 licenselink = "https://github.com/yihui/hugo-xmin/blob/master/LICENSE.md"
 description = "eXtremely Minimal Hugo theme: about 150 lines of code in total, including HTML and CSS"
 homepage = "https://xmin.yihui.org"
+demosite = "https://xmin.yihui.org"
 tags = ["minimal", "blog", "personal", "clean", "simple", "starter", "minimalist"]
 features = ["blog"]
 min_version = "0.18"