feat: emit AiderTerminalOpen event when terminal is created

[colout]

Hi,

I was looking for a way to add shortcuts that are only applied to this specific buffer. I wanted to use escape to close in normal mode, and <c-s> in all modes, but only in the aider terminal buffer.

Rather than fussing around with checking buffer names in an autocmd, I found it easier to just emit a User event in the plugin on my branch and use the following code in my LazyVim:

  {
   "GeorgesAlkhouri/nvim-aider",
   init = function()
     vim.api.nvim_create_autocmd("User", {
       pattern = "AiderTerminalOpen",
       callback = function(args)
         local buf = args.data.buf
         vim.keymap.set("n", "<Esc>", function()
           require("nvim_aider.terminal").toggle()
         end, { buffer = buf, silent = true })

         vim.keymap.set({"t", "n", "i", "v"}, "<c-s>", function()
           require("nvim_aider.terminal").toggle()
         end, { buffer = buf, silent = true })
       end,
     })
   end,

Not sure if you find this at all helpful, but if you do feel free to merge this (or supply any feedback and I'll happily make the change).

This has been my favorite nvim aider plugin for its simplicity, and I'm happy to contribute more if you're supporting it.

This PR was written 100% by aider / claude sonnet, including the readme. Keeping with the plugin theme, no code was written by a human, though this pr description is 100% me.

[GeorgesAlkhouri]

Thanks for your PR! I really appreciate you taking the time to contribute. I'll make sure to review this over the weekend. Really cool to hear that you're finding the plugin useful.

[GeorgesAlkhouri]

Thanks again for your contribution! The idea of emitting user events brings flexibility to the plugin architecture, I really like it! Would you be interested in extending this approach by adding a closing event to provide a more generalized solution? Also, the README could replace its keymap section with an events section that includes keymaps as examples.