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/nostr_utils/mod.rs

@@ -102,7 +102,7 @@ impl NostrClient {
 
     /// Initializes a new [`NostrClient`] instance and connects to the specified
     /// relays.
-    pub async fn init(options: &CliOptions) -> Self {
+    pub async fn init(options: &CliOptions, relays: &[RelayUrl]) -> Self {
         let client = Self::new(
             Client::builder()
                 .signer(Keys::new(
@@ -115,7 +115,7 @@ impl NostrClient {
                 .build(),
         );
 
-        client.add_relays(&options.relays).await;
+        client.add_relays(relays).await;
         client
     }