Adding fix for publishing recipes to ECR (radius-project#7887)

# Description

ECR thorws following error when Data is nil, updating the data to a
empty descriptor.
```
Something went wrong Cause: PUT "
https://<account-name>.dkr.ecr.us-east-2.amazonaws.com/v2/test-private-ecr/blobs/uploads/47552bfb-e8f7-41ad-9c07-310446dc14?digest=sha256%3Ae3b0c44298fc1c149afbf4c8996fb927ae41e4649b934ca495991b7852b855":
response status code 400: blob upload invalid: The upload with id '47552bfb-e8f7-41ad-9c07-314186dc14' in the repository with name 'test-ecr' in registry with id '<account-name>' cannot be completed because it does not have any parts.
```

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Fixes: radius-project#7855

---------

Signed-off-by: Vishwanath Hiremath <vhiremath@microsoft.com>

pkg/cli/cmd/bicep/publish/publish.go

@@ -237,7 +237,10 @@ func (r *Runner) prepareSource(ctx context.Context) (*memory.Store, error) {
 	}
 
 	// Push config blob
-	configDesc, err := pushBlob(ctx, configMediaType, nil, src)
+	// Set blob content to an empty descriptor instead of nil as some registries that implement the OCI image manifest specification,
+	// such as AWS ECR, do not support pushing empty content.
+	// Ref: https://git.homegu.com/devcontainers/cli/issues/814
+	configDesc, err := pushBlob(ctx, configMediaType, []byte("{}"), src)
 	if err != nil {
 		return nil, err
 	}