Support exporting current container to image (#1172)

This PR adds a command to export container to image (#1019).

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

## Motivation and Context
Users can export their container to image.

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

Sources/ContainerCommands/Application.swift

@@ -63,6 +63,7 @@ public struct Application: AsyncLoggableCommand {
                     ContainerStats.self,
                     ContainerStop.self,
                     ContainerPrune.self,
+                    ContainerExport.self,
                 ]
             ),
             CommandGroup(