LibVT: Allow updating the window progress via an escape sequence

You can now request an update of the terminal's window progress by
sending this escape sequence:

<esc>]9;<value>;<max_value>;<escape><backslash>

I'm sure we can find many interesting uses for this! :^)

Libraries/LibVT/TerminalWidget.cpp

@@ -47,6 +47,7 @@
 #include <LibGfx/Font.h>
 #include <LibGfx/Palette.h>
 #include <errno.h>
+#include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -361,6 +362,14 @@ void TerminalWidget::paint_event(GUI::PaintEvent& event)
     }
 }
 
+void TerminalWidget::set_window_progress(int value, int max)
+{
+    float float_value = value;
+    float float_max = max;
+    float progress = (float_value / float_max) * 100.0f;
+    window()->set_progress((int)roundf(progress));
+}
+
 void TerminalWidget::set_window_title(const StringView& title)
 {
     if (!Utf8View(title).validate()) {