New command tagtypes available

Shows the list of tag types configured by the ``metadata_to_use`` setting.

src/TagPrint.cxx

@@ -18,6 +18,14 @@ tag_print_types(Response &r) noexcept
 			r.Fmt(FMT_STRING("tagtype: {}\n"), tag_item_names[i]);
 }
 
+void
+tag_print_types_available(Response &r) noexcept
+{
+	for (unsigned i = 0; i < TAG_NUM_OF_ITEM_TYPES; i++)
+		if (global_tag_mask.Test(TagType(i)))
+			r.Fmt(FMT_STRING("tagtype: {}\n"), tag_item_names[i]);
+}
+
 void
 tag_print(Response &r, TagType type, std::string_view value) noexcept
 {