extract some keys to the plugin configs

lua/setup/aerial.lua

@@ -1,5 +1,5 @@
 require('aerial').setup({
-  backends = { 'lsp', 'treesitter','markdown' },
+  backends = { 'lsp', 'treesitter', 'markdown' },
   layout = {
     default_direction = "prefer_left"
   },
@@ -7,4 +7,12 @@ require('aerial').setup({
   show_guides = true,
 })
 require('telescope').load_extension('aerial')
-vim.keymap.set('n', '<leader>s', '<cmd>AerialToggle<cr>', opts)
+require('legendary').keymaps(
+  {
+    {
+      '<leader>s',
+      ':AerialToggle<CR>',
+      description = 'Symbols outline',
+    }
+  }
+)