Add a minimal example for a python script to display PNG images

See #1080

docs/graphics-protocol.rst

@@ -75,6 +75,47 @@ You can also use the *CSI t* escape code to get the screen size. Send
 ``<ESC>[4;<height>;<width>t`` where *height* and *width* are the window size in
 pixels. This escape code is supported in many terminals, not just kitty.
 
+A minimal example
+------------------
+
+Some minimal python code to display PNG images in kitty, using the most basic
+features of the graphics protocol:
+
+.. code-block:: python
+
+   import sys
+   from base64 import standard_b64encode
+
+   def serialize_gr_command(cmd, payload=None):
+      cmd = ','.join('{}={}'.format(k, v) for k, v in cmd.items())
+      ans = []
+      w = ans.append
+      w(b'\033_G'), w(cmd.encode('ascii'))
+      if payload:
+         w(b';')
+         w(payload)
+      w(b'\033\\')
+      return b''.join(ans)
+
+   def write_chunked(cmd, data):
+      data = standard_b64encode(data)
+      while data:
+         chunk, data = data[:4096], data[4096:]
+         m = 1 if data else 0
+         cmd['m'] = m
+         sys.stdout.buffer.write(serialize_gr_command(cmd, chunk))
+         sys.stdout.flush()
+         cmd.clear()
+
+   write_chunked({'a': 'T', 'f': 100}, open(sys.argv[-1], 'rb').read())
+
+
+Save this script as :file:`png.py`, then you can use it to display any PNG
+file in kitty as::
+
+   python png.py file.png
+
+
 The graphics escape code
 ---------------------------