Update documentation for mathjax

Author: azerupi

book-example/book.toml

@@ -1,3 +1,6 @@
 title = "mdBook Documentation"
 description = "Create book from markdown files. Like Gitbook but implemented in Rust"
 author = "Mathieu David"
+
+[output.html]
+mathjax-support = true

book-example/src/format/mathjax.md

@@ -1,20 +1,30 @@
 # MathJax Support
 
-mdBook supports math equations through [MathJax](https://www.mathjax.org/).
+mdBook has optional support for math equations through [MathJax](https://www.mathjax.org/).
 
-**However the normal method for indication math equations with `$$` does not work (yet?).**
+To enable MathJax, you need to add the `mathjax-support` key to your `book.toml` under the `output.html` section.
 
-To indicate an inline equation \\( \int x = \frac{x^2}{2} \\) use
+```toml
+[output.html]
+mathjax-support = true
 ```
-\\( \int x = \frac{x^2}{2} \\)
+
+>**Note:**  
+The usual delimiters MathJax uses are not yet supported. You can't currently use `$$ ... $$` as delimiters and the `\[ ... \]` delimiters need an extra backslash to work. Hopefully this limitation will be lifted soon.
+
+### Inline equations
+Inline equations are delimited by `\\[` and `\\]`. So for example, to render the following inline equation \\( \int x dx = \frac{x^2}{2} + C \\) you would write the following:
+```
+\\( \int x dx = \frac{x^2}{2} + C \\)
 ```
 
-To indicate a block equation
+### Block equations
+Block equations are delimited by `\\[` and `\\]`. To render the following equation
 
 \\[ \mu = \frac{1}{N} \sum_{i=0} x_i \\]
 
 
-use
+you would write:
 
 ```bash
 \\[ \mu = \frac{1}{N} \sum_{i=0} x_i \\]