Sections with unreserverd characters will appear url-encoded and need to
be unescaped before using it.
Wikipedia generates 2 different spans in this case in the same page, one
with an id resulting of replacing the % symbols with . and the other with
the decoded version of the string. For example, for /wiki/foo#A%C3%A1A it
will generate:
<span id="A.C3.A1A"></span>
<span id="AáA">AáA</span>
Unescaping the `m_url_hash_name` should work in all cases to target the
proper section span.
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