Fix broken link in README (#15)

Signed-off-by: Daniel Villanueva <davillan@redhat.com>

Author: danivilla9

README.md

@@ -24,7 +24,7 @@ The [OpenShift Local Extension](https://github.com/crc-org/crc-extension) enable
 
 ### ✨ Sandbox
 
-The [OpenShift Developer Sandbox Extension] helps you learn containers, Kubernetes, and OpenShift in your browser using [Developer Sandbox](https://developers.redhat.com/developer-sandbox) for free.
+The [OpenShift Developer Sandbox Extension](https://github.com/redhat-developer/podman-desktop-sandbox-ext) helps you learn containers, Kubernetes, and OpenShift in your browser using [Developer Sandbox](https://developers.redhat.com/developer-sandbox) for free.
 
 ### ✨ OpenShift Checker
 
@@ -36,4 +36,4 @@ You can install the Red Hat Extension Pack directly inside of Podman Desktop. Si
 
 ![image](https://raw.githubusercontent.com/redhat-developer/podman-desktop-redhat-pack-ext/main/screenshots/install.png)
 
-Alternatively, you can use the container image `ghcr.io/redhat-developer/podman-desktop-redhat-pack-ext:nightly` to install nightly version of the Extension pack.
+Alternatively, you can use the container image `ghcr.io/redhat-developer/podman-desktop-redhat-pack-ext:nightly` to install nightly version of the Extension pack.