feature: add support for GLFM math blocks

This add supports for GLFM's math blocks [1] using hugo's Markdown
render hooks [2].

[1]: https://docs.gitlab.com/ee/user/markdown.html#math
[2]: https://gohugo.io/templates/render-hooks/#render-hooks-for-code-blocks

Signed-off-by: Stephan Lachnit <stephanlachnit@debian.org>

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

@@ -0,0 +1,3 @@
+<p>```math
+{{ .Inner | safeHTML }}
+```</p>

userguide/content/en/docs/Adding content/diagrams-and-formulae/index.md

@@ -35,6 +35,13 @@ $$\tag*{(1)} P(E) = {n \choose k} p^k (1-p)^{n-k}$$
 The probability of getting \\(k\\) heads when flipping \\(n\\) coins is:
 $$\tag*{(1)}  P(E) = {n \choose k} p^k (1-p)^{n-k}$$
 
+You can also use [GLFM's math blocks](https://docs.gitlab.com/ee/user/markdown.html#math):
+````markdown
+```math
+E = m c^2
+```
+````
+
 {{% alert title="Tip" %}}
 This [wiki page](https://en.wikibooks.org/wiki/LaTeX/Mathematics) provides in-depth information about typesetting mathematical formulae using the \\(\LaTeX\\) typesetting system.
 {{% /alert %}}
@@ -86,6 +93,10 @@ errorColor = "#CD5C5C"
   left = "\\["
   right = '\\]'
   display = true
+[[params.katex.options.delimiters]]
+  left = "```math"
+  right = '```'
+  display = true
 ```
 
 For a complete list of options and their detailed description, have a look at the documentation of \\({\KaTeX}'s\\) [Rendering API options](https://katex.org/docs/autorender.html#api) and of \\({\KaTeX}'s\\) [configuration options](https://katex.org/docs/options.html).