Add ability to intercept streams with middleware

Add the ability to add support for such things as zmodem and/or other
stream middleware's

term.go

@@ -84,6 +84,7 @@ type Terminal struct {
 	printData          []byte
 	printer            Printer
 	cmd                *exec.Cmd
+	middleware         Middleware
 }
 
 // Printer is used for spooling print data when its received.
@@ -266,8 +267,12 @@ func (t *Terminal) open() error {
 	if err != nil {
 		return err
 	}
-	t.in = in
-	t.out = out
+
+	t.in, t.out = in, out
+	if t.middleware != nil {
+		t.out, t.in = t.middleware.SetupMiddleware(out, in)
+	}
+
 	t.pty = pty
 
 	t.updatePTYSize()
@@ -353,8 +358,10 @@ func (t *Terminal) RunWithConnection(in io.WriteCloser, out io.Reader) error {
 	for t.config.Columns == 0 { // don't load the TTY until our output is configured
 		time.Sleep(time.Millisecond * 50)
 	}
-	t.in = in
-	t.out = out
+	t.in, t.out = in, out
+	if t.middleware != nil {
+		t.out, t.in = t.middleware.SetupMiddleware(out, in)
+	}
 
 	t.run()
 
@@ -497,3 +504,20 @@ func (t *Terminal) Dragged(d *fyne.DragEvent) {
 func (t *Terminal) DragEnd() {
 	t.selecting = false
 }
+
+// SetMiddleware sets the middleware function that will be used when creating a new terminal.
+// The middleware function is responsible for setting up the I/O readers and writers.
+func (t *Terminal) SetMiddleware(mw Middleware) {
+	t.middleware = mw
+}
+
+// Middleware is an interface that defines the methods required to set up
+// the input (reader) and output (writer) streams for the terminal.
+// Implementations of this interface can modify or wrap the reader and writer.
+type Middleware interface {
+	// SetupMiddleware configures the input and output streams for the terminal.
+	// It takes an input reader (r) and an output writer (w) as arguments.
+	// The function returns a possibly modified reader and writer that
+	// the terminal will use for I/O operations.
+	SetupMiddleware(r io.Reader, w io.WriteCloser) (io.Reader, io.WriteCloser)
+}