fix: wrong backreference in excluded content (#56)

As Ruby substitution functions (i.e `sub` and `gsub`) support regex.
Hence, the backreference of substitution will be performed, so that
we should escape any backreference of the substitution (i.e. "\0"
to "\\0" ).

Author: jeffreytse

lib/jekyll-spaceship/cores/processor.rb

@@ -192,7 +192,10 @@ def post_exclude(content)
       while @exclusion_store.size > 0
         match = @exclusion_store.pop
         id = @exclusion_store.size
-        content = content.sub("<!JEKYLL@#{object_id}@#{id}>", match)
+        content = content.sub(
+          "<!JEKYLL@#{object_id}@#{id}>",
+          match.gsub(/(\\\d)/,'\\\\\1')
+        )
       end
       @exclusion_store = []
       content