DOC add authors and release date to whats_new/0.23
<ul class="sk-landing-call-list list-unstyled">
<li><strong>On-going development:</strong>
<a href="https://scikit-learn.org/dev/whats_new.html"><strong>What's new</strong> (Changelog)</a>
+ <li><strong>May 2020.</strong> scikit-learn 0.23.0 is available for download (<a href="whats_new/v0.23.html#version-0-23-0">Changelog</a>).
</li>
<li><strong>Scikit-learn from 0.23 requires Python 3.6 or greater.</strong>
</li>
</li>
<li><strong>May 2019.</strong> scikit-learn 0.21.0 to 0.21.2 are available for download (<a href="whats_new/v0.21.html#version-0-21-2">Changelog</a>).
</li>
- <li><strong>March 2019.</strong> scikit-learn 0.20.3 is available for download (<a href="whats_new/v0.20.html#version-0-20-3">Changelog</a>).
- </li>
- <li><strong>September 2018.</strong> scikit-learn 0.20.0 is available for download (<a href="whats_new/v0.20.html#version-0-20-0">Changelog</a>).
- </li>
- <li><strong>July 2018.</strong> scikit-learn 0.19.2 is available for download (<a href="whats_new/v0.19.html#version-0-19-2">Changelog</a>).
- </li>
- <li><strong>July 2017.</strong> scikit-learn 0.19.0 is available for download (<a href="whats_new/v0.19.html#version-0-19">Changelog</a>).
- </li>
</ul>
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