docs: add session_child_cycle and session_child_cycle_reverse keybinds (#3807)

packages/web/src/content/docs/keybinds.mdx

@@ -23,6 +23,8 @@ OpenCode has a list of keybinds that you can customize through the OpenCode conf
     "session_unshare": "none",
     "session_interrupt": "escape",
     "session_compact": "<leader>c",
+    "session_child_cycle": "ctrl+right",
+    "session_child_cycle_reverse": "ctrl+left",
     "messages_page_up": "pageup",
     "messages_page_down": "pagedown",
     "messages_half_page_up": "ctrl+alt+u",