feat: add RawMsg and Raw command to print raw strings to the terminal

This adds a new message type, `RawMsg`, and a new command, `Raw`, that
allows printing raw strings to the terminal without any intermediate
processing.

input.go

@@ -51,5 +51,5 @@ func translateInputEvent(e input.Event) Msg {
 	case input.TerminalVersionEvent:
 		return TerminalVersionMsg(e)
 	}
-	return nil
+	return e
 }

raw.go

@@ -0,0 +1,15 @@
+package tea
+
+// RawMsg is a message that contains a string to be printed to the terminal
+// without any intermediate processing.
+type RawMsg struct {
+	Msg any
+}
+
+// Raw is a command that prints the given string to the terminal without any
+// formatting.
+func Raw(r any) Cmd {
+	return func() Msg {
+		return RawMsg{r}
+	}
+}

tea.go

@@ -662,6 +662,9 @@ func (p *Program) eventLoop(model Model, cmds chan Cmd) (Model, error) {
 			case requestCursorPosMsg:
 				p.execute(ansi.RequestCursorPosition)
 
+			case RawMsg:
+				p.execute(fmt.Sprint(msg.Msg))
+
 			case setCursorPosMsg:
 				p.renderer.moveTo(msg.X, msg.Y)