Add example testcases for CommentSyntax option in Scaladoc

Those consist of packages example.comment.md and example.comment.wiki
configured with a matching comment syntax.

Author: jchyb

project/Build.scala

@@ -1801,6 +1801,10 @@ object ScaladocConfigs {
       .add(Revision("main"))
       .add(SnippetCompiler(List("scaladoc-testcases/docs=compile")))
       .add(SiteRoot("scaladoc-testcases/docs"))
+      .add(CommentSyntax(List(
+        "scaladoc-testcases/src/example/comment-md=markdown",
+        "scaladoc-testcases/src/example/comment-wiki=wiki"
+      )))
       .add(ExternalMappings(List(dottyExternalMapping, javaExternalMapping)))
       .withTargets(tastyRoots)
   }

project/scripts/cmdScaladocTests

@@ -35,6 +35,7 @@ dist/target/pack/bin/scaladoc \
   "-skip-by-id:scala.runtime.stdLibPatches" \
   "-skip-by-id:scala.runtime.MatchCase" \
   "-snippet-compiler:scaladoc-testcases/docs=compile" \
+  "-comment-syntax:scaladoc-testcases/src/example/comment-md=markdown,scaladoc-testcases/src/example/comment-wiki=wiki" \
   -siteroot scaladoc-testcases/docs \
   -project-footer "Copyright (c) 2002-2022, LAMP/EPFL" \
   -default-template static-site-main \

scaladoc-testcases/src/example/comment-md/CommentExample.scala

@@ -0,0 +1,6 @@
+package example.comment.md
+/**
+ * # markdown header
+ * Markdown syntax is used here.
+ */
+object CommentExample

scaladoc-testcases/src/example/comment-wiki/CommentExample.scala

@@ -0,0 +1,6 @@
+package example.comment.wiki
+/**
+ * = wiki header =
+ * Wiki syntax is used here.
+ */
+object CommentExample