Fix: indigo footnotes ref link (#9)

Change-Id: Id3fad1540081d65fabc35b0e6c8782ce4353dd77

Author: elonz

src/themes/mweb-indigo.scss

@@ -201,10 +201,6 @@ pre::before {
   width: 100%;
 }
 
-.footnote-backref {
-  display: none;
-}
-
 .footnotes {
   padding-top: 0.5rem;
   padding-bottom: 0.5rem;