Add barebones of tito shortcode logic

I want to be able to add a shortcode for tito and add specific named
params in order to display the tito widget on a page I wish.

I also want to allow use of releases and discount-codes

The current naming convention is using underscores so lets do that!
We'll also move to using external css and js, rather than keep them
locally we don't want to add extra work always updating these.

Signed-off-by: Chris Mills <me@christophermills.co.uk>

Author: Christopher Mills

REFERENCE.md

@@ -1,5 +1,4 @@
 # Reference for devopsdays-theme
-
 # Table of contents
 <!-- MDTOC maxdepth:6 firsth1:0 numbering:0 flatten:0 bullets:0 updateOnSave:1 -->
 
@@ -307,3 +306,25 @@ This shortcode allows for the embedding of a Google form on a page, in a manner
 ```
 {{< google_form "https://docs.google.com/forms/d/e/1FAIpQLScvv-ty_wEBlYkJaEC1OU0qqqbIHjf9JVa-Ptdo5TcHqz5EDA/viewform?usp=sf_link" >}}
 ```
+
+### tito_widget
+
+Using the tito shortcode enables the embedding of the tito sales widget described on their documentation (https://ti.to/docs/widget). To use it you just need to enter to event path of your tito event which will follow the URL of your event page. For example, if the URL is `https://ti.to/devopsdays-london/2019` your event path would be `devlopsdays-london/2019`. The shortcode also enables the other features described such as the ability to show specific tickets using the examples shown below
+
+```
+{{< tito_widget event="devopsdays-london/2019" >}}
+```
+
+To show only a specific ticket within the widget:
+
+```
+{{< tito_widget event="devopsdays-london/2019" releases="fiaurhghf2k">}}
+```
+
+To show discounted tickets on the page (they display as a striked through full-price along with the new price):
+
+```
+{{< tito_widget event="devopsdays-london/2019" discount-code="examplediscount" >}}
+```
+
+

layouts/shortcodes/tito_widget.html

@@ -0,0 +1,4 @@
+<script src='https://js.tito.io/v1' async></script>
+<link rel="stylesheet" type="text/css" href='https://css.tito.io/v1.1' />
+<tito-widget event="{{ .Get "event"  }}" {{ if (.Get "releases") }} releases="{{ with .Get "releases" }}{{.}}{{ end }}"{{ end }} {{ if (.Get "discount-code" )}} discount-code="{{ with .Get "discount-code" }}{{ . }}{{ end }}"{{ end }}></tito-widget>
+