adding priority to erb nav (#221)

Author: Scott McAllister

website/pagerduty.erb

@@ -19,6 +19,9 @@
                 <li<%= sidebar_current("docs-pagerduty-datasource-extension-schema") %>>
                     <a href="/docs/providers/pagerduty/d/extension_schema.html">pagerduty_extension_schema</a>
                 </li>
+                <li<%= sidebar_current("docs-pagerduty-datasource-priority") %>>
+                    <a href="/docs/providers/pagerduty/d/priority.html">pagerduty_priority</a>
+                </li>                
                 <li<%= sidebar_current("docs-pagerduty-datasource-schedule") %>>
                     <a href="/docs/providers/pagerduty/d/schedule.html">pagerduty_schedule</a>
                 </li>