add an empty sri field

data/assets.toml

@@ -17,6 +17,7 @@
   url = "https://cdnjs.cloudflare.com/ajax/libs/highlight.js/%s/highlight.min.js"
 [js.mathJax]
   version = "3"
+  sri = ""
   url = "https://cdn.jsdelivr.net/npm/mathjax@%s/es5/tex-chtml.js"
 [js.isotope]
   version = "3.0.6"