Docs: Add settings to index

Fix rst formatting

Author: pszpetkowski

docs/source/index.rst

@@ -4,12 +4,13 @@
    contain the root `toctree` directive.
 
 Welcome to django-templated-mail documentation!
-==================================
+===============================================
 
 .. toctree::
    :maxdepth: 2
 
    getting_started
+   settings
 
 Indices and tables
 ==================

docs/source/settings.rst

@@ -9,7 +9,7 @@ You may optionally provide following settings:
     'SITE_NAME': 'Foo Website',
 
 DOMAIN
---------------------------
+------
 
 Used in email template context. In most cases it is used to simplify building URLs,
 when frontend and backend are hosted under different address'. If not provided
@@ -19,7 +19,7 @@ the current site's domain will be used.
 **Required**: ``False``
 
 SITE_NAME
----------------------
+---------
 
 Used in email template context. Usually it will contain the desired title of your
 app. If not provided the current site's name will be used.