chore(lib): update katex 0.15.3 -> 0.15.6

assets/lib/VERSION

@@ -13,7 +13,7 @@ lightgallery@2.4.0 https://github.com/sachinchoolur/lightgallery
 clipboard.js@2.0.11 https://github.com/zenorocha/clipboard.js
 sharer.js@0.4.0 https://github.com/ellisonleao/sharer.js
 typeit@8.5.4 https://github.com/alexmacarthur/typeit
-katex@0.15.3 https://katex.org/
+katex@0.15.6 https://katex.org/
 mermaid@9.1.0 https://github.com/mermaid-js/mermaid
 echarts@5.3.2 https://echarts.apache.org/
 mapbox-gl@2.8.2 https://github.com/mapbox/mapbox-gl-js

assets/lib/katex/contrib/copy-tex.min.css

@@ -1 +1 @@
-.katex,.katex-display{-webkit-user-select:all;-moz-user-select:all;user-select:all}
+.katex,.katex-display{-webkit-user-select:all;-moz-user-select:all;user-select:all}