feat(manifest): adds missing entries in manifest

[doppelganger9]

Contents

Adding a few entries to show what is possible:

• dir
• lang
• scope
• description
• orientation
• related_applications
• prefer_related_applications

Reference:

• https://www.w3.org/TR/appmanifest/#example-manifests

Discussion

I don't know if the convention is to hide entries with default values or to show them for anyone to see what is possible. Both options have pros/cons.

You be the judge 👍