feat: add CTRL+[ binding as <Esc> alias

in Vim/Neovim there is alias for `<Esc>` mapping -- `<C-[>`. it is useful if
your `<Esc>` key is hard to hit on your keyboard.

for reference:

    https://vimhelp.org/insert.txt.html#i_CTRL-%5B
    https://neovim.io/doc/user/insert.html#i_CTRL-%5B

atuin/src/command/client/search/interactive.rs

@@ -196,6 +196,11 @@ impl State {
             KeyCode::Esc if !(self.tab_index == 0 && self.keymap_mode == KeymapMode::VimInsert) => {
                 return Self::handle_key_exit(settings);
             }
+            KeyCode::Char('[')
+                if ctrl && !(self.tab_index == 0 && self.keymap_mode == KeymapMode::VimInsert) =>
+            {
+                return Self::handle_key_exit(settings);
+            }
             KeyCode::Tab => {
                 return InputAction::Accept(self.results_state.selected());
             }
@@ -320,7 +325,7 @@ impl State {
                 _ => {}
             },
             KeymapMode::VimInsert => {
-                if input.code == KeyCode::Esc {
+                if input.code == KeyCode::Esc || (ctrl && input.code == KeyCode::Char('[')) {
                     self.set_keymap_cursor(settings, "vim_normal");
                     self.keymap_mode = KeymapMode::VimNormal;
                     return InputAction::Continue;