Merge pull request #15903 from michael-k/patch-1

Updated license links

docs/_includes/footer.html

@@ -6,7 +6,7 @@
 
     <p>Designed and built with all the love in the world by <a href="https://twitter.com/mdo" target="_blank">@mdo</a> and <a href="https://twitter.com/fat" target="_blank">@fat</a>.</p>
     <p>Maintained by the <a href="https://github.com/orgs/twbs/people">core team</a> with the help of <a href="https://github.com/twbs/bootstrap/graphs/contributors">our contributors</a>.</p>
-    <p>Code licensed under <a href="https://github.com/twbs/bootstrap/blob/master/LICENSE" target="_blank">MIT</a>, documentation under <a href="https://creativecommons.org/licenses/by/3.0/">CC BY 3.0</a>.</p>
+    <p>Code licensed under <a rel="license" href="https://github.com/twbs/bootstrap/blob/master/LICENSE" target="_blank">MIT</a>, documentation under <a rel="license" href="https://creativecommons.org/licenses/by/3.0/" target="_blank">CC BY 3.0</a>.</p>
     <ul class="bs-docs-footer-links text-muted">
       <li>Currently v{{ site.current_version }}</li>
       <li>&middot;</li>