docs: example toggle keymap

Author: NickvanDyke

README.md

@@ -41,6 +41,7 @@ https://github.com/user-attachments/assets/4dd19151-89e4-4272-abac-6710dbc6edc1
     vim.keymap.set({ "n", "x" }, "<C-a>", function() require("opencode").ask("@this: ", { submit = true }) end, { desc = "Ask opencode" })
     vim.keymap.set({ "n", "x" }, "<C-x>", function() require("opencode").select() end, { desc = "Execute opencode action…" })
     vim.keymap.set({ "n", "x" }, "ga",    function() require("opencode").prompt("@this") end, { desc = "Add to opencode" })
+    vim.keymap.set("n", "<C-.>",   function() require("opencode").toggle() end, { desc = "Toggle opencode" })
     vim.keymap.set("n", "<S-C-u>", function() require("opencode").command("messages_half_page_up") end, { desc = "opencode half page up" })
     vim.keymap.set("n", "<S-C-d>", function() require("opencode").command("messages_half_page_down") end, { desc = "opencode half page down" })
     -- You may want these if you stick with the opinionated "<C-a>" and "<C-x>" above — otherwise consider "<leader>o".