Consider adding shortcuts for decrypting and copying to clipboard

I find this tool very useful, big thanks for it.

2 features would make life easier for me:

• press Ctrl+Shift+d to decrypt clipboard contents
• automaticaly copy the decrypted text to the clipboard

Similary, Ctrl+Shift+E could Encrypt clipboard contents and Ctrl+Shift+A could add the key from the clipboard to the keyring.

Copied from Tails bug tracker #12466