docs: null-ls for neovim

Author: kamadorueda

integrations/neovim/README.md

@@ -2,6 +2,7 @@
 
 In order to use Alejandra with
 [Neovim](https://neovim.io/)
-please use the
-[neoformat](https://github.com/sbdchd/neoformat)
-plugin.
+please use any of the following plugins:
+
+- [Neoformat](https://github.com/sbdchd/neoformat)
+- [null-ls.nvim](https://github.com/jose-elias-alvarez/null-ls.nvim)