ReadFile or ScpGet

Have you consider adding a new method to copy a file from a remote ssh server to the client?

Could be implemented by adding a method to the `MakeConfig` struct, names could be `ReadFile` or `ScpGet`.

#### Proposed Method Signature:

```go
func (ssh_conf *MakeConfig) ReadFile(remoteFile string) (io.Reader, error)
// OR
func (ssh_conf *MakeConfig) ScpGet(remoteFile string) (io.Reader, error)
```

This method would establish an SSH session, execute the necessary remote command (like `cat` or internal SFTP/SCP logic), and return an `io.Reader`.

This pattern would allow handling the output efficiently using standard Go I/O utilities, like copying directly to a local file:

```go
reader, err := ssh.ReadFile("/remote/path/file.dat")
if err != nil { /* ... */ }

// Copy the remote stream directly to a local file
localFile, err := os.Create("/local/path/file.dat")
if err != nil { /* ... */ }
defer localFile.Close()

_, err = io.Copy(localFile, reader)
```

Happy to do submit PR myself if this is something you'd like to add to the library.

Start by locating the MakeConfig struct and the existing SSH session or command-handling entry points in the library. Compare the proposed ReadFile and ScpGet APIs, then define the remote-file streaming behavior and error handling; the work is done when one supported method copies a remote file through an io.Reader and has corresponding coverage.

Written by the indexing model from the issue text.