add Direnv to the integrations (#10675)

related to
- direnv/direnv#1175

# Description
this PR adds to the list of integrations of Nushell the new Direnv
section introduced in direnv/direnv#1175
🥳

# User-Facing Changes

# Tests + Formatting

# After Submitting

README.md

@@ -220,6 +220,7 @@ Please submit an issue or PR to be added to this list.
 -   [atuin](https://github.com/ellie/atuin)
 -   [clap](https://github.com/clap-rs/clap/tree/master/clap_complete_nushell)
 -   [Dorothy](http://github.com/bevry/dorothy)
+-   [Direnv](https://github.com/direnv/direnv/blob/master/docs/hook.md#nushell)
 
 ## Contributing