Fix/serialize close html tag (#9437)

* fix: should use tree.isSelfClosing || isVoidElement

* docs: about html

* fix: Void element without self-closing slash (e.g., <br> instead of <br/>)

* Update editions/test/tiddlers/tests/data/serialize/VoidElements.tid

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

editions/test/tiddlers/tests/data/serialize/VoidElements.tid

@@ -0,0 +1,12 @@
+tags: $:/tags/wikitext-serialize-test-spec
+title: Serialize/VoidElements
+type: text/vnd.tiddlywiki
+
+This tests void elements like <br/> and <br> (without `/`).
+
+Line one<br>Line two
+Line three<br/>Line four
+
+<hr>
+
+Images are also void: <img src="test.png">

editions/tw5.com/tiddlers/releasenotes/5.4.0/#8258.tid

@@ -23,6 +23,7 @@ There is also a utility `serializeAttribute` for a single attribute node, like a
 * Separate serialize handlers for each WikiText rule as `module-type: wikiruleserializer`
 * Test suite with tag `$:/tags/wikitext-serialize-test-spec`
 * It uses each parser's name as rule (`nextMatch.rule.name`), each AST node that needs serialization has a `type` property matching the rule name
+** HTML tags and widgets are handled by the `html` serializer
 
 !! Example Usage
 

plugins/tiddlywiki/wikitext-serialize/rules/html.js

@@ -16,9 +16,13 @@ exports.serialize = function(tree,serialize) {
 	// Children
 	var children = tree.children ? serialize(tree.children) : "";
 	var result = "";
+	var isVoidElement = $tw.config.htmlVoidElements.indexOf(tag) !== -1;
 	// Self-closing tag
 	if(tree.isSelfClosing) {
 		result += "<" + tag + (attributes ? " " + attributes : "") + "/>";
+	} else if(isVoidElement) {
+		// Void element without self-closing slash (e.g., <br> instead of <br/>)
+		result += "<" + tag + (attributes ? " " + attributes : "") + ">";
 	} else {
 		// Opening and closing tags
 		result += "<" + tag + (attributes ? " " + attributes : "") + ">" + children + "</" + tag + ">";