feat(nixvim): add opencode plugin

- Added opencode plugin
- Added keymaps for opencode actions (<leader>oa, <leader>ox, <leader>og)
- Included lsof package for opencode.nvim to function

home/modules/cli/nixvim/plugins/opencode.nix

@@ -0,0 +1,16 @@
+{ pkgs, ...}:
+
+{
+  home.packages = with pkgs; [
+    lsof
+  ];
+  programs.nixvim = {
+    plugins.opencode = {
+      enable = true;
+      settings = {
+        auto_reload = true;
+      };
+    };
+    opts.autoread = true;
+  };
+}