Add S-Tab mapping to outdent

Update Copilot to use C-a to accept change to avoid conflict with `Tab` for indenting

.config/nvim/lua/plugins/llm.lua

@@ -1,6 +1,14 @@
 return {
 	{
 		"github/copilot.vim",
+		config = function()
+			vim.keymap.set("i", "<C-a>", 'copilot#Accept()', {
+				expr = true,
+				silent = true,
+        replace_keycodes = false,
+			})
+			vim.g.copilot_no_tab_map = true
+		end,
 	},
 	{
 		"CopilotC-Nvim/CopilotChat.nvim",