Fix groupping entries using markdown syntax

Author: pikinier20

scaladoc-testcases/src/example/groups.scala

@@ -0,0 +1,23 @@
+package example
+
+/** Groups
+ * @groupname foo Foo-group
+ * @groupdesc bar Description of group
+ * bar
+ */
+class Groups {
+  /** Method in group foo
+   * @group foo
+   */
+  def groupFoo: String = ???
+
+  /** Method in group bar
+   * @group bar
+   */
+  def groupBar: String = ???
+
+  /** Method in group bazz
+   * @group bazz
+   */
+  def groupBazz: String = ???
+}

scaladoc/src/dotty/tools/scaladoc/tasty/comments/Comments.scala

@@ -178,7 +178,7 @@ class MarkdownCommentParser(repr: Repr)(using dctx: DocContext)
   def stringToMarkup(str: String) =
     MarkdownParser.parseToMarkdown(str, markdown.DocFlexmarkParser(resolveLink))
 
-  def markupToString(t: mdu.Node): String = t.toString()
+  def markupToString(t: mdu.Node): String = t.getChars().toString()
 
   def markupToDokka(md: mdu.Node): DocPart = md