docs: Add a few more words of intro to the tutorial.
Tutorial
========
+Welcome to EdgeDB!
+
+This tutorial covers the steps needed to set up EdgeDB and start using
+it. This is a good starting point if you're new to EdgeDB.
+
* Start with the :ref:`ref_tutorial_install`
* Set up your :ref:`ref_tutorial_createdb`
* Learn the basics about :ref:`ref_tutorial_queries`
