[META] Implement chunked transport for WebRTC DataChannel / Image Clipboards

[ehfd]

The issue #43 has been patched by #73, but the core issue is that there is no graceful handling for a DataChannel message which is above the size of 65535 bytes.

Therefore, it would be VERY useful to implement chunked messages for DataChannels, as the benefit can be applicable to any workload which can use DataChannel messages between the client and server using WebRTC.

If implemented, remove the restrictions placed by:

selkies-gstreamer/src/selkies_gstreamer/gstwebrtc_app.py

Line 758 in 1f2070b

# TODO: WebRTC DataChannel accepts a maximum length of 65489 (= 65535 - 46 for '{"type": "clipboard", "data": {"content": ""}}'), remove this restriction after implementing DataChannel chunking

Moreover, more diverse formats of clipboards (including images) can be supported, but is not practical unless chunked DataChannels are implemented. xclip provides this capability explicitly but has been sidelined in favor to xsel because of a long-standing bug. It should be manually parsed to base64 with the image type and reconstruct it in either side.

[ehfd]

https://groups.google.com/g/discuss-webrtc/c/f3dfmu3oh00