support comments (jsonc) in app manifests

[goyalyashpal]

as comments help a lot:

• say in commenting out the details for the architectures u don't use in local manifests
  as this will help reduce unnecessary package downloads for updating hashes of those
• for adding blank keys while creating new manifests by hand
• to add any upcoming changes in the app manifest - but while it is not landed in upstream stable yet
• to add any detail worth paying attention to
• etc etc.

[rashil2000]

Please update this thread: #2715

[goyalyashpal]

i had read that before, but jsonc is not entirely different thing. it's just json with comments no?