I'm an avid tmux+neovim user, too, though working with Reason is a lot easier in VS Code. Making the switch from actual vim to fake vim (ie JS emulation) sucks. Recently, VSCodeVim merged #1725 to add actual neovim as an editor - it's using NeoVim's embedding API so you're using neovim to edit the text file inside of VSCode's chrome, including all of VSCode's type hints and popups. Info here: https://github.com/VSCod…
If 20 years ago you would have told me we gonna have Vim inside a text editor inside a web browser I would have thought you are insane.