feat: add logo variants (#2)

* feat: add favicon

* feat: add white logo

Author: Adam Butterworth

README.rst

@@ -34,8 +34,19 @@ Files this package must make available
 ``/logo-trademark.svg`` A variant of the logo with a trademark ® or ™. Note: This file must be present. If you don't have a trademark variant of your logo, copy your regular logo and use that.
 
 .. image:: /logo-trademark.svg
-    :alt: edX
+    :alt: logo
+    :width: 128px
+
+``/logo-white.svg`` A variant of the logo for use on dark backgrounds
+
+.. image:: /logo-white.svg
+    :alt: logo
     :width: 128px
 
+``/favicon.ico`` A site favicon
+
+.. image:: /favicon.ico
+    :alt: favicon
+    :width: 32px
 
 ``/paragon/fonts.scss``, ``/paragon/_variables.scss``, ``/paragon/_overrides.scss``  A SASS theme for `@edx/paragon <https://github.com/edx/paragon>`_. Theming documentation in Paragon is coming soon. In the meantime, you can start a theme by the contents of `_variables.scss (after line 7) <https://github.com/edx/paragon/blob/master/scss/core/_variables.scss#L7-L1046>`_ file from the Paragon repository into this file.