Add banner image credits for v5.2.1

See https://talk.tiddlywiki.org/t/the-banner-designer-should-be-acknowledged-in-the-whats-new-section/1787

cc @ibnishak

editions/tw5.com/tiddlers/releasenotes/Release 5.2.1.tid

@@ -12,6 +12,12 @@ type: text/vnd.tiddlywiki
 
 //[[See GitHub for detailed change history of this release|https://github.com/Jermolene/TiddlyWiki5/compare/v5.2.0...v5.2.1]]//
 
+<<.banner-credits
+	credit:"""Congratulations to [[Mohammad Rahmani|https://github.com/kookma]] and [[Elise Springer|https://www.wesleyan.edu/academics/faculty/espringer/profile.html]] for their winning design for the banner for this release (here are the [[other entries|https://groups.google.com/g/tiddlywiki/c/GU0TPGNMPvw/m/y1SyQk_nAQAJ]]).
+"""
+	url:"https://raw.githubusercontent.com/Jermolene/TiddlyWiki5/cb43b91ab6b14c2a16af917cfab0e5b2371502c6/editions/tw5.com/tiddlers/images/New%20Release%20Banner.png"
+>>
+
 ! Highlights
 
 !! <<.link-badge-added "https://github.com/Jermolene/TiddlyWiki5/pull/6168">> New Filter Cascade Mechanism

editions/tw5.com/tiddlers/system/doc-macros.tid

@@ -147,4 +147,14 @@ This is an example tiddler. See [[Table-of-Contents Macros (Examples)]].
 </$tiddler>
 \end
 
+\define .banner-credits(credit,url)
+<img src=<<__url__>> width="140" style="float:left;margin-right:0.5em;"/>
+
+$credit$
+
+<div style="clear:both;">
+
+</div>
+\end
+
 <pre><$view field="text"/></pre>