Following requests directly from the site, I found out how to enable AutoScan for Github Repository automatically.
So, sharing script to make it publicly available and I hope it will help someone:
curl --include \ --request POST \ --header "Content-Type: application/x-www-form-urlencoded" \ -u ${SONAR_TOKEN}: \ --data-binary "installationKeys=${GITHUB_ORG}%2F${REPO_NAME}%7C${REPO_ID}&organization=${SONAR_ORG}" \ "https://sonarcloud.io/api/alm_integration/provision_projects"
curl --include \ -u ${SONAR_TOKEN}: \ "https://sonarcloud.io/api/autoscan/eligibility?autoEnable=true&projectKey=${GITHUB_ORG}_${REPO_NAME}"
Thanks a lot.