feat: implement command mode

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/hyperlog-tui/src/commands.rs

@@ -0,0 +1,31 @@
+use crate::models::Msg;
+
+pub trait IntoCommand {
+    fn into_command(self) -> Command;
+}
+
+impl IntoCommand for () {
+    fn into_command(self) -> Command {
+        Command::new(|| None)
+    }
+}
+
+impl IntoCommand for Command {
+    fn into_command(self) -> Command {
+        self
+    }
+}
+
+pub struct Command {
+    func: Box<dyn FnOnce() -> Option<Msg>>,
+}
+
+impl Command {
+    pub fn new<T: FnOnce() -> Option<Msg> + 'static>(f: T) -> Self {
+        Self { func: Box::new(f) }
+    }
+
+    pub fn execute(self) -> Option<Msg> {
+        self.func.call_once(())
+    }
+}