feat: use external nio

BREAKING CHANGE: Requires https://github.com/nvim-neotest/nvim-nio to be
installed

Author: rcarriga

README.md

@@ -9,26 +9,28 @@ good out of the box configuration.
 
 ## Installation
 
-Install with your favourite package manager alongside nvim-dap
+Install with your favourite package manager alongside nvim-dap and nvim-nio
 
 [**dein**](https://github.com/Shougo/dein.vim):
 
 ```vim
 call dein#add("mfussenegger/nvim-dap")
+call dein#add("nvim-neotest/nvim-nio")
 call dein#add("rcarriga/nvim-dap-ui")
 ```
 
 [**vim-plug**](https://github.com/junegunn/vim-plug)
 
 ```vim
 Plug 'mfussenegger/nvim-dap'
+Plug 'nvim-neotest/nvim-nio'
 Plug 'rcarriga/nvim-dap-ui'
 ```
 
 [**packer.nvim**](https://github.com/wbthomason/packer.nvim)
 
 ```lua
-use { "rcarriga/nvim-dap-ui", requires = {"mfussenegger/nvim-dap"} }
+use { "rcarriga/nvim-dap-ui", requires = {"mfussenegger/nvim-dap", "nvim-neotest/nvim-nio"} }
 ```
 
 It is highly recommended to use [neodev.nvim](https://github.com/folke/neodev.nvim) to enable type checking for nvim-dap-ui to get