[gnome-software.wiki] Update Software metadata

[Philip Withnall <pwithnall src gnome org>]

commit 7961768a91ff3442469a77f400daba3dbefaf4ec
Author: Philip Withnall <philip tecnocode co uk>
Date:   Fri Aug 20 18:30:27 2021 +0000

    Update Software metadata

 Software-metadata.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/Software-metadata.md b/Software-metadata.md
index 7d2ce97..aa2e7db 100644
--- a/Software-metadata.md
+++ b/Software-metadata.md
@@ -111,7 +111,8 @@ If some metadata is missing for an application, GNOME Software can only guess wh
 How to add missing links
 ---
 
-TODO
+ - Add all relevant types from https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-url
+ - TODO
 
 How to add missing hardware information
 ---