add markdown dialect (WIP) & add strikethrough and underline font styles

src/graphics/ui/gui_xml.cpp

@@ -278,6 +278,9 @@ static std::shared_ptr<UINode> readLabel(
     if (element.has("text-wrap")) {
         label->setTextWrapping(element.attr("text-wrap").asBool());
     }
+    if (element.has("markdown")) {
+        label->setMarkdown(element.attr("markdown").asBool());
+    }
     return label;
 }
 
@@ -381,6 +384,9 @@ static std::shared_ptr<UINode> readTextBox(UiXmlReader& reader, const xml::xmlel
     if (element.has("line-numbers")) {
         textbox->setShowLineNumbers(element.attr("line-numbers").asBool());
     }
+    if (element.has("markdown")) {
+        textbox->setMarkdown(element.attr("markdown").asBool());
+    }
     if (element.has("consumer")) {
         textbox->setTextConsumer(scripting::create_wstring_consumer(
             reader.getEnvironment(),