Treat center like a block-level element

Fixes Python-Markdown#1481

Author: facelessuser

docs/changelog.md

@@ -23,7 +23,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   as they are parsed outside of "markdown" blocks giving a more consistent
   expectation to external extensions (#1503).
 * `md_in_html` handle tags within inline code blocks better (#1075).
-* `md_in_html` fix handling of one-liner block HTML handling (#1074)
+* `md_in_html` fix handling of one-liner block HTML handling (#1074).
+* Ensure `<center>` is treated like a block-level element.
 
 ## [3.7] -- 2024-08-16
 

markdown/util.py

@@ -54,7 +54,8 @@
     # Other elements which Markdown should not be mucking up the contents of.
     'canvas', 'colgroup', 'dd', 'body', 'dt', 'group', 'html', 'iframe', 'li', 'legend',
     'math', 'map', 'noscript', 'output', 'object', 'option', 'progress', 'script',
-    'style', 'summary', 'tbody', 'td', 'textarea', 'tfoot', 'th', 'thead', 'tr', 'video'
+    'style', 'summary', 'tbody', 'td', 'textarea', 'tfoot', 'th', 'thead', 'tr', 'video',
+    'center'
 ]
 """
 List of HTML tags which get treated as block-level elements. Same as the `block_level_elements`