api/media/ev3dev: add Image/screen save method

This was overlooked previously.

doc/api/hubs_ev3brick.inc

@@ -176,6 +176,9 @@
 
     .. autoattribute:: pybricks.hubs::EV3Brick.screen.height
 
+    .. automethod:: pybricks.hubs::EV3Brick.screen.save
+
+
     .. rubric:: Using the battery
 
     .. automethod:: pybricks.hubs::EV3Brick.battery.voltage

doc/api/media.rst

@@ -306,5 +306,6 @@ with image files using the ``Image`` class given below.
     .. automethod:: pybricks.media.ev3dev.Image.load_image
 
 
+    .. rubric:: Saving the image
 
-
+    .. automethod:: pybricks.media.ev3dev.Image.save

pybricks/media/ev3dev.py

@@ -218,6 +218,20 @@ class Image:
                 There was a problem allocating a new image.
         """
 
+    def save(self, filename):
+        """Saves |this image| as a ``.png`` file.
+
+        Arguments:
+            filename (str):
+                The path to the file to be saved.
+
+        Raises:
+            TypeError:
+                ``filename`` is not a string.
+            OSError:
+                There was a problem saving the file.
+        """
+
 
 class Font:
     """Object that represents a font for writing text."""