update Docker documentation

Signed-off-by: muraca <mmuraca247@gmail.com>

README.md

@@ -16,17 +16,20 @@ The flag `-- --nocapture` can be used to print the execution times for proof gen
 The single circuits can be tested by matching the test name with `sudoku`, `permutation` or `factorial`.
 The tests that match the `mock` pattern are written using the `MockProver` struct, while the others use the custom real-world provers.
 
-### Running via docker
-To run the tests via docker, the simplest way is to build the docker image:
+### Running via Docker
+To run the tests via Docker, the simplest way is to use the image published by CI:
 ```bash
-docker build -t halo2-playground .
+docker run --rm --network host ghcr.io/libecciolabs/halo2-playground:main
 ```
-and then run the tests:
+
+You can always build the docker image yourself:
 ```bash
+git clone https://github.com/LibeccioLabs/Halo2-Playground/
+docker build -t halo2-playground ./Halo2-Playground/
 docker run --rm halo2-playground
 ```
 
-It will run `cargo test --release` inside the docker container, so you can append any other flag, including a match for the tests you want to run.
+Since the Docker image will run `cargo test --release`, you can append any other flag, including a match for the tests you want to run.
 For example, to run only the tests in the `sudoku` module, you can run:
 ```bash
 docker run --rm halo2-playground sudoku