Add Mathjax to rustdoc output

when generating local documentation, this requires `RUSTDOCFLAGS=--html-in-header docs/mathjax.html` for math to be rendered.

Cargo.toml

@@ -9,3 +9,9 @@ edition = "2021"
 generic_parameterize = "0.1.0"
 itertools = "0.10.5"
 num-traits = "0.2.15"
+
+[package.metadata.docs.rs]
+rustdoc-args = [
+    "--html-in-header",
+    "doc/mathjax.html",
+]

docs/mathjax.html

@@ -0,0 +1,11 @@
+<script type="text/x-mathjax-config">
+  MathJax.Hub.Config({
+    asciimath2jax: {
+        delimiters: [['$','$']]
+    }
+  });
+</script>
+
+<script type="text/javascript" async
+        src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.7/MathJax.js?config=TeX-MML-AM_CHTML">
+</script>