Fix showtitle

Author: ia3andy

asciidoc-java/src/main/java/io/yupiik/asciidoc/renderer/html/AsciidoctorLikeHtmlRenderer.java

@@ -296,8 +296,12 @@ public void visitParagraph(final Paragraph element) {
 
     @Override
     public void visitHeader(final Header header) {
-        if (header.attributes().get("notitle") == null &&
-                !header.title().isBlank()) {
+        var showTitle = Boolean.parseBoolean(header.attributes().getOrDefault("showtitle", "false"))
+                        && !header.attributes().containsKey("notitle");
+        var noHeader = Boolean.parseBoolean(configuration.getAttributes().getOrDefault("noheader", "false"));
+
+        // showTitle has priority over noHeader (noTitle and showTitle are supposed to be mutually exclusive)
+        if ((showTitle || !noHeader) && !header.title().isBlank()) {
             builder.append(" <h1>").append(escape(header.title())).append("</h1>\n");
         }