fix: link to getting started guide from downloads page

Author: ErikBjare

downloads.pug

@@ -23,6 +23,8 @@ article.container
         | {% endfor %}
     | {% endfor %}
 
+  div For help on how to get started, see the #[a(href="https://docs.activitywatch.net/en/latest/getting-started.html") Getting Started guide] in the documentation.
+
   div Looking for an older or pre-release version? You can find all #[a(href="https://github.com/ActivityWatch/activitywatch/releases") releases on GitHub].
 
   h3.mt-3 Nightly builds