feat: Support relays and naddrs sets

This commit introduces support for 'sets', a feature that simplifies
referencing multiple relays or naddrs with a single word.

Sets are stored in the config directory under `n34` as `config.toml` in
`TOML` format. The config path follows the `$XDG_CONFIG_HOME` standard,
defaulting to `$HOME/.config` if unset.

The `n34 sets` command allows managing sets, adding, removing, updating,
or displaying them. When using the main `--relays` flag, a set name can
be provided to automatically expand its relays (an error occurs if the
set contains no relays). Similarly, any command accepting naddrs can
reference a set to extract its naddrs.

Sets can also be merged by updating a set while specifying another
set in `--repo` merges their naddrs, while `--set-relays` merges their
relays. Removal follows the same pattern.

Signed-off-by: Awiteb <a@4rs.nl>

src/cli/mod.rs

@@ -15,16 +15,23 @@
 // along with this program. If not, see <https://gnu.org/licenses/gpl-3.0.html>.
 
 /// Commands module
-mod commands;
+pub mod commands;
+/// The CLI config
+pub mod config;
+/// Default lazy values for CLI arguments
+pub mod defaults;
 /// CLI arguments parsers
 pub mod parsers;
 /// CLI traits
-mod traits;
+pub mod traits;
+/// Common helper types used throughout the CLI.
+pub mod types;
 
 use clap::Parser;
 use clap_verbosity_flag::Verbosity;
 
 pub use self::commands::*;
+pub use self::config::*;
 use self::traits::CommandRunner;
 use crate::error::N34Result;