Add katex

documentation/katex.markdown

@@ -2,14 +2,18 @@
 
 KaTeX is a fast math typesetting library for the web. It uses javascript for client-side rendering.
 
-## Example
+## Example usage
 
 <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.10.0-beta/dist/katex.min.css" integrity="sha384-9tPv11A+glH/on/wEu99NVwDPwkMQESOocs/ZGXPoIiLE8MU/qkqUcZ3zzL+6DuH" crossorigin="anonymous">
 <script src="https://cdn.jsdelivr.net/npm/katex@0.10.0-beta/dist/katex.min.js" integrity="sha384-U8Vrjwb8fuHMt6ewaCy8uqeUXv4oitYACKdB0VziCerzt011iQ/0TqlSlv8MReCm" crossorigin="anonymous"></script>
 <script src="https://cdn.jsdelivr.net/npm/katex@0.10.0-beta/dist/contrib/auto-render.min.js" integrity="sha384-aGfk5kvhIq5x1x5YdvCp4upKZYnA8ckafviDpmWEKp4afOZEqOli7gqSnh8I6enH" crossorigin="anonymous"></script>
 
+`This $\int\limits_1^\infty \frac{1}{k}\,dk$ is inline.` results in:
+
 This $\int\limits_1^\infty \frac{1}{k}\,dk$ is inline.
 
+`This $$f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x} \,d\xi$$ not.` results in:
+
 This $$f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x} \,d\xi$$ not.
 
 <script>