Rewrite Mermaid and KaTeX to be usable both from shorcode and code block, update dependencies

layouts/_default/_markup/render-codeblock-katex.html

@@ -0,0 +1,13 @@
+{{- if not (.Page.Store.Get "katex") -}}
+<!-- Include katex only first time -->
+<link rel="stylesheet" href="{{ "katex/katex.min.css" | relURL }}" />
+<script defer src="{{ "katex/katex.min.js" | relURL }}"></script>
+{{ with resources.Get "katex.json" }}
+<script defer src="{{ "katex/auto-render.min.js" | relURL }}" onload="renderMathInElement(document.body, {{ .Content | safeJS }});"></script>
+{{ end }}
+{{- .Page.Store.Set "katex" true -}}
+{{- end -}}
+
+{{- with .Inner }}
+<span>\[ {{ . }} \]</span>
+{{ end -}}