improvement: use clap for command line args

src/cli.rs

@@ -0,0 +1,14 @@
+use clap::Parser;
+
+#[derive(Parser)]
+#[command(about = "A nostr relay written in Rust", author = env!("CARGO_PKG_AUTHORS"), version = env!("CARGO_PKG_VERSION"))]
+pub struct CLIArgs {
+    #[arg(
+        short,
+        long,
+        help = "Use the <directory> as the location of the database",
+        default_value = ".",
+        required = false
+    )]
+    pub db: String,
+}