neovim: update README to mention $NVIM_BIN

types/neovim/README.md

@@ -7,7 +7,7 @@ The `vim.d.tl` file is autogenerated by the `autogen` shell script that does the
 
 So to add types, rather than directly modifying `vim.d.tl` modify `template` which will be used to generate `vim.d.tl`
 
-Ideally, the version you generate the types for should be the latest stable version. The cool kids that run the latest dev branch can handle generating their own types :)
+Ideally, the version you generate the types for should be the latest stable version. The cool kids that run the latest dev branch can handle generating their own types :). (You can ensure this by using the environment variable `$NVIM_BIN` for the autogen script)
 
 ## Some notes