Add image to readme

Author: codingjoe

README.rst

@@ -1,13 +1,19 @@
+.. raw:: html
+
+    <p align="center">
+      <picture>
+        <source media="(prefers-color-scheme: dark)" srcset="https://github.com/codingjoe/django-mail-auth/raw/main/images/logo-dark.svg">
+        <source media="(prefers-color-scheme: light)" srcset="https://github.com/codingjoe/django-mail-auth/raw/main/images/logo-light.svg">
+        <img alt="Django MailAuth: Secure login links; no passwords required!" src="https://github.com/codingjoe/django-mail-auth/raw/main/images/logo-light.svg">
+      </picture>
+    </p>
+
 ================
 Django Mail Auth
 ================
 
 |version| |docs| |coverage| |license|
 
-.. figure:: sample.png
-    :width: 425
-    :alt: screenshot from a login form
-
 Django Mail Auth is a lightweight authentication backend for Django,
 that does not require users to remember passwords.
 
@@ -19,6 +25,10 @@ Django Mail Auth features:
 - drop in Wagtail login replacement
 - extendable SMS support
 
+.. figure:: sample.png
+    :width: 425
+    :alt: screenshot from a login form
+
 This project was inspired by:
 
 - `Is it time for password-less login?`_ by `Ben Brown`_