[Initiatives.wiki] Update App Metadata

[Tobias Bernard <tbernard src gnome org>]

commit 0f76b7c3278ec5dab00a4a051799d29fd853fddf
Author: Tobias Bernard <tbernard gnome org>
Date:   Mon Jun 8 11:02:04 2020 +0000

    Update App Metadata

 App-Metadata.md | 40 +++++++++++++++++++++++++---------------
 1 file changed, 25 insertions(+), 15 deletions(-)
---
diff --git a/App-Metadata.md b/App-Metadata.md
index f72c6c9..e45918c 100644
--- a/App-Metadata.md
+++ b/App-Metadata.md
@@ -1,17 +1,3 @@
-Areas covered by the initiative:
-
-Appstream:
-  * Summary
-  * Description
-  * Developer name
-  * Various links
-  * Release notes
-  * Screenshots
-
-Repository Metadata:
-  * README
-  * Repository icon
-
 ## Summary
 
 The summary should answer the question **"What superpower does this app give me?"**. It doesn't need to 
comprehensively describe everything the app does, as long as it highlights one important aspect and makes it 
clear why it's valuable.
@@ -48,8 +34,32 @@ Bad Examples:
 
 ## Developer name
 
+[Appstream 
documentation](https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-developer_name
+)
+
 ## Links
 
 ## Release Notes
 
-## Screenshots
\ No newline at end of file
+[Appstream 
documentation](https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-releases)
+
+## Screenshots
+
+General guidance:
+- Provide multiple screenshots showing off the main areas of the app
+- Show off the app with realistic and good-looking example content
+- Update screenshots when the app UI changes
+- Use GNOME system defaults (stylesheet, font, icons, window decorations, etc.)
+
+Avoid:
+- Using a non-standard system stylesheet or icons
+- Using non-standard window decorations (e.g. minimize/maximize enabled)
+
+
+[Appstream 
documentation](https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-screenshots)
+
+## README
+
+## Repository Icon
+
+The Gitlab repository icon should be the regular app icon with a baked-in shadow. We have plans to add a way 
to automatically export a PNG with a baked-in shadow from App Icon Preview for this purpose.
\ No newline at end of file