feat(validation): footnotes in HTML 5.2

[Kristinita]

1. Summary

It would be nice, if would be possible use valid HTML instead of obsolete rel/ref footnotes.

2. Argumentation

I get errors in HTML5 validator:

Bad value “footnote” for attribute “rel” on element “a”: The string “footnote” is not a registered keyword.
The “rev” attribute on the “a” element is obsolete. Use the “rel” attribute instead, with a term having the opposite meaning.

No rel/rev in official footnotes recommendation.

See similar issue for details.

3. Data

I have Kira__PythonMarkdown--Footnotes.md file, it content:

Kira[^1]

[^1]: Goddess

4. Steps to reproduce

python -m markdown -x footnotes Kira__PythonMarkdown--Footnotes.md

5. Expected behavior

For example, as recommended in Stack Overflow.

6. Actual behavior

<p>Kira<sup id="fnref:1"><a class="footnote-ref" href="#fn:1" rel="footnote">1</a></sup></p>
<div class="footnote">
<hr />
<ol>
<li id="fn:1">
<p>Goddess&#160;<a class="footnote-backref" href="#fnref:1" rev="footnote" title="Jump back to footnote 1 in the text">&#8617;</a></p>
</li>
</ol>
</div>

7. Environment

• Windows 10 Enterprise LTSB 64-bit EN
• Python 3.7.1
• Python Markdown 3.0.1

Thanks.

[waylan]

This is a duplicate of #723, which was fixed in #728 and will be available in the next release.

[Kristinita]

@waylan , when will the new release be approximately released? Thanks.

[waylan]

When it’s ready. We have a few outstanding PRs waiting for a final review. I expect a release will be ready once those are finalized.