Add warning note on finding docs for release versions (apple#676)

## Type of Change
- [ ] Bug fix
- [ ] New feature  
- [ ] Breaking change
- [x] Documentation update

## Motivation and Context
Closes apple#638. This PR adds a
warning in the README for the documentation links to help newcomers find
the correct documentation based on the version of `container` they are
running.

## Testing
- [ ] Tested locally
- [ ] Added/updated tests
- [x] Added/updated docs

Signed-off-by: Kathryn Baldauf <[email protected]>

Author: katiewasnothere

README.md

@@ -58,6 +58,11 @@ uninstall-container.sh -k
 - [Build and run](./BUILDING.md) `container` on your own development system.
 - View the project [API documentation](https://apple.github.io/container/documentation/).
 
+> [!IMPORTANT]
+> The links above are for the CURRENT BRANCH's documentation. To find documentation for official releases, find the target release on the [Release Page](https://github.com/apple/container/releases) and click the tag corresponding to your release version. 
+>
+> Example: [release 0.4.1 tag](https://github.com/apple/container/tree/0.4.1)
+
 ## Contributing
 
 Contributions to `container` are welcomed and encouraged. Please see our [main contributing guide](https://github.com/apple/containerization/blob/main/CONTRIBUTING.md) for more information.