Bump css-what from 2.1.0 to 2.1.3 in /demo

Bumps [css-what](https://github.com/fb55/css-what) from 2.1.0 to 2.1.3.
- [Release notes](https://github.com/fb55/css-what/releases)
- [Commits](fb55/css-what@v2.1.0...v2.1.3)

---
updated-dependencies:
- dependency-name: css-what
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

demo/yarn.lock

@@ -2441,8 +2441,9 @@ css-url-regex@^1.1.0:
   resolved "http://registry.npm.taobao.org/css-url-regex/download/css-url-regex-1.1.0.tgz#83834230cc9f74c457de59eebd1543feeb83b7ec"
 
 css-what@2.1:
-  version "2.1.0"
-  resolved "http://registry.npm.taobao.org/css-what/download/css-what-2.1.0.tgz#9467d032c38cfaefb9f2d79501253062f87fa1bd"
+  version "2.1.3"
+  resolved "https://registry.yarnpkg.com/css-what/-/css-what-2.1.3.tgz#a6d7604573365fe74686c3f311c56513d88285f2"
+  integrity sha512-a+EPoD+uZiNfh+5fxw2nO9QwFa6nJe2Or35fGY6Ipw1R3R4AGz1d1TEZrCegvw2YTmZ0jXirGYlzxxpYSHwpEg==
 
 cssesc@^0.1.0:
   version "0.1.0"