docs: add initial documentation for criu-image-streamer

Signed-off-by: Manogna Polikepad <manognapolikepad@gmail.com>

Author: manognapolikepad-lab

Documentation/image-streamer.txt

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+## criu-image-streamer
+
+### Overview
+criu-image-streamer is an optional helper component used with CRIU to stream checkpoint images instead of writing them entirely to disk before transfer.
+
+It is built and installed separately from CRIU and is typically used in workflows where reducing downtime or disk I/O is important.
+
+### When is criu-image-streamer used?
+criu-image-streamer can be used when checkpoint images need to be transferred efficiently, for example during migration scenarios where writing full image sets to disk may be slow or undesirable.
+
+### Difference from live migration
+Unlike traditional live migration, criu-image-streamer does not continuously synchronize memory pages. Instead, it focuses on streaming CRIU checkpoint images during the checkpoint/restore process.
+
+### Installation
+The CRIU repository provides a helper script to install criu-image-streamer:
+
+`scripts/install-criu-image-streamer.sh`
+
+This script installs the Rust toolchain, clones the criu-image-streamer repository, and builds the project.
+
+### References
+- scripts/install-criu-image-streamer.sh
+- https://github.com/checkpoint-restore/criu-image-streamer
+
+
+Internally, CRIU and criu-image-streamer communicate using a simple request–reply protocol to coordinate image transfer during dump and restore.