[No QA][TS migration] Migrate 'reviewerChecklist.js', 'getReleaseBody.js', 'getPreviousVersion.js' and 'checkDeployBlockers.js' .github files to Typescript

[No QA][TS migration] Migrate 'reviewerChecklist.js', 'getReleaseBody.js', 'getPreviousVersion.js' and 'checkDeployBlockers.js' .github files to Typescript #276