Add add-host to the root README

Author: stuartleeks

README.md

@@ -11,6 +11,7 @@ If you want to create your own features, see <https://github.com/devcontainers/f
 | Feature                                                      | Description                                                       |
 | ------------------------------------------------------------ | ----------------------------------------------------------------- |
 | [azure-cli-persistence](src/azure-cli-persistence/README.md) | Preserve `~/.azure` folder across instances (avoids extra logins) |
+| [add-host](src/add-host/README.md)                           | Add a host name/ip to the dev container hosts file                |
 | [dev-tunnels](src/dev-tunnels/README.md)                     | Set up the `devtunnel` CLI for working with Dev Tunnels           |
 | [shell-history](src/shell-history/README.md)                 | Preserve shell history across dev container instances/rebuilds    |