Signed-off-by: Andreas Auernhammer <github@aead.dev>

This commit adds support for private keys that are not protected
by a password. The `PrivateKey` type now supports text (un)marshaling
to en/decode a non-encrypted text representation.

The `minisign` command now accepts a `-W` flag for generating a private
key without requiring a password.

…licKey`

This commit improves the documentation for the core minisign types and
improves the implementation for various functions. It also adds an
additional test vector for (un)marshaling private keys.

Signed-off-by: Andreas Auernhammer <github@aead.dev>

This commit adds the `-C` flag for changing private key passwords.
It also improves the entire minisign command implementation, removes
some redunant code and fixes minor tui issues.

This commit adjusts and simplifies the private key tests slightly.

Signed-off-by: Andreas Auernhammer <github@aead.dev>

Signed-off-by: Andreas Auernhammer <github@aead.dev>