doc: add note about advanced luasnip features

Author: tjdevries

init.lua

@@ -711,6 +711,9 @@ require('lazy').setup({
               luasnip.jump(-1)
             end
           end, { 'i', 's' }),
+
+          -- For more advanced luasnip keymaps (e.g. selecting choice nodes, expansion) see:
+          --    https://github.com/L3MON4D3/LuaSnip?tab=readme-ov-file#keymaps
         },
         sources = {
           { name = 'nvim_lsp' },