feat: Add Dockerfile and Github Action.

This will allow CI for creating Docker images on push.
Should be changed from push to pull_request once we feel more
comfortable with the solution.

Author: Eran Davidovich

.github/workflows/docker-image.yml

@@ -24,7 +24,7 @@ jobs:
         with:
           platforms: linux/amd64
           push: true
-          tags: ${{ secrets.DOCKERHUB_USERNAME }}/pyth-client-py:{{ git_sha }} # should be tagged latest later on
+          tags: ${{ secrets.DOCKERHUB_USERNAME }}/pyth-client-py:{{ GITHUB_SHA }} # should be tagged latest later on
 
       - name: Image digest
         run: echo ${{ steps.docker_build.outputs.digest }}