Add customization.md

docs/customization.md

@@ -0,0 +1,9 @@
+# Customizing Soapbox
+
+Soapbox supports customization of the user interface, to allow per instance branding and other features.  Current customization features include:
+* Instance name
+* Site logo
+* Favicon
+* About page
+* Terms of Service page
+* Promo panel list items, e.g. blog site link