epub converter: add internal links processing2

src/html_epub_preprocessor.py

@@ -241,6 +241,8 @@ def unwrap_structural_tags(body_tag):
     # should be before other tags processing, not to remove converter empty tags with id
     # not all cases, if span has <p>s and NavigableString, it won't unwrap
     for s in body_tag.find_all("span"):
+        if s.attrs.get('epub:type') == 'pagebreak':
+            continue
         if s.contents:
             is_not_struct_tag = [child.name not in structural_tags_names for child in s.contents]
             if all(is_not_struct_tag):