docs: mention nodenv in README.md

PR-URL: #2698
Credit: @RA80533
Close: #2698
Reviewed-by: @darcyclarke

Author: RA80533

README.md

@@ -27,6 +27,7 @@ If you're looking to manage multiple versions of **`node`** &/or **`npm`**, cons
 * [**`nave`**](https://github.com/isaacs/nave)
 * [**`n`**](https://github.com/tj/n)
 * [**`volta`**](https://github.com/volta-cli/volta)
+* [**`nodenv`**](https://github.com/nodenv/nodenv)
 
 ### Usage