feat: Added input for pull and push on docker build

[christian-kreuzberger-dtx]

This PR

• Adds the two input fields PUSH and PULL to the docker build action

This allows more advanced workflow configuration, e.g.:

      - name: Docker Build
        id: docker_build
        uses: keptn/gh-automation/.github/actions/docker-build@main
        with:
          TAGS: |
            ghcr.io/${{ github.repository_owner }}/${{ env.IMAGE }}:${{ env.VERSION }}
            ${{ env.DOCKER_ORGANIZATION }}/${{ env.IMAGE_INITCONTAINER }}:${{ env.VERSION }}
          BUILD_ARGS: |
            version=${{ env.VERSION }}
            datetime=${{ env.DATETIME }}
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          REGISTRY_USER: ${{ secrets.REGISTRY_USER }}
          REGISTRY_PASSWORD: ${{ secrets.REGISTRY_PASSWORD }}
          PUSH: (github.event_name == 'push' || github.event_name == 'workflow_dispatch' || github.event.pull_request.head.repo.full_name == github.repository)