Unescape special characters (boostorg#1839)

Author: gregjkal

core/htmlhelper.py

@@ -1,4 +1,5 @@
 import re
+from html import unescape
 
 from bs4 import BeautifulSoup, Comment, Tag
 from django.template.loader import render_to_string
@@ -259,6 +260,7 @@ def slightly_modernize_legacy_library_doc_page(content):
             el.getparent().remove(el)
 
     content = html.tostring(root, encoding="unicode", method="html")
+    content = unescape(content)  # avoid escaping special characters like ń
     return content.replace("https://www.boost.org/doc/libs/", "/doc/libs/")