Add information about CI to README (use-ink#343)

* added information about ci to readme

* added link to local ci docs

* Trim long line

Co-authored-by: Hernando Castano <hernando@hcastano.com>

README.md

@@ -51,25 +51,27 @@ More relevant links:
 
 * Step 3: `cargo install --force cargo-contract`
 
-### Docker Image
+### Installation using Docker Image
 
 If you prefer to use Docker instead we have a Docker image
 [available on the Docker Hub](https://hub.docker.com/r/paritytech/contracts-ci-linux):
 
 ```bash
-# Pull the latest image.
-docker pull  paritytech/contracts-ci-linux
+# Pull the latest stable image.
+docker pull paritytech/contracts-ci-linux:production
 
 # Create a new contract in your current directory.
-docker run --rm -it -v $(pwd):/sources paritytech/contracts-ci-linux \
+docker run --rm -it -v $(pwd):/sources paritytech/contracts-ci-linux:production \
   cargo +nightly contract new --target-dir /sources my_contract
 
 # Build the contract. This will create the contract file under
 # `my_contract/target/ink/my_contract.contract`.
-docker run --rm -it -v $(pwd):/sources paritytech/contracts-ci-linux \
+docker run --rm -it -v $(pwd):/sources paritytech/contracts-ci-linux:production \
   cargo +nightly contract build --manifest-path=/sources/my_contract/Cargo.toml
 ```
 
+If you want to reproduce other steps of CI process you can use the following
+[guide](https://github.com/paritytech/scripts#reproduce-ci-locally).
 
 ## Usage