Feature Request: Desktop application UI to work with PGP

❤️ Keybase team
To make it easier for non-technical users to work with PGP encryption functionality of Keybase, it would be great to add PGP encrypt/decrypt capability to Desktop UI.
At the moment, one have to direct users to open their terminals and use cli commands, which is somewhat frightening to less technical users.
```
keybase pgp decrypt -i encrypted_file.txt.asc
```

The issue names no files or tests; begin with the existing `keybase pgp decrypt -i encrypted_file.txt.asc` CLI flow and determine which desktop UI entry point should expose it. Done would require a defined desktop workflow for both PGP encryption and decryption without terminal commands, including an agreed scope and validation path.

Written by the indexing model from the issue text.