feat: Sync UrwidImageScreen with lock_tty()

- Add: Synchronize the following I/O methods of `UrwidImageScreen`
  with `.utils.lock_tty()`:

  - `get_available_raw_input()`
  - `flush()`
  - `write()`

Refs: #73, #80

src/term_image/widget/urwid.py

@@ -10,7 +10,13 @@
 
 from ..exceptions import UrwidImageError
 from ..image import BaseImage, ITerm2Image, KittyImage, Size, TextImage, kitty
-from ..utils import BEGIN_SYNCED_UPDATE, END_SYNCED_UPDATE, COLOR_RESET_b, ESC_b
+from ..utils import (
+    BEGIN_SYNCED_UPDATE,
+    END_SYNCED_UPDATE,
+    COLOR_RESET_b,
+    ESC_b,
+    lock_tty,
+)
 
 # NOTE: Any new "private" attribute of any subclass of an urwid class should be
 # prepended with "_ti" to prevent clashes with names used by urwid itself.
@@ -533,6 +539,21 @@ def draw_screen(self, maxres, canvas):
             self.write(END_SYNCED_UPDATE)
             self.flush()
 
+    @lock_tty
+    def flush(self):
+        """See the baseclass' method for the description."""
+        return super().flush()
+
+    @lock_tty
+    def get_available_raw_input(self):
+        """See the baseclass' method for the description."""
+        return super().get_available_raw_input()
+
+    @lock_tty
+    def write(self, data):
+        """See the baseclass' method for the description."""
+        return super().write(data)
+
     def _start(self, *args, **kwargs):
         ret = super()._start(*args, **kwargs)
         if KittyImage._forced_support or KittyImage.is_supported():