feat(plugins): add omp.nvim plugin and toggle keybinding

lua/plugins/omp.lua

@@ -0,0 +1,8 @@
+-- omp.nvim: streams the active file / cursor line / visual selection to a
+-- running Oh My Pi session over a unix socket. Needs the OMP-side extension
+-- (`omp plugin install omp.nvim`). Toggle bind: <C-a><C-a> in astrocore.lua.
+return {
+  "rauls-kjarners/omp.nvim",
+  event = "VeryLazy",
+  config = function() require("omp").setup() end,
+}