Addd 8.18 and 8.19 manifests (#362) (#364)

(cherry picked from commit c121f9a)

Co-authored-by: Jorge Sanz <[email protected]>

Author: github-actions[bot]

scripts/constants.js

@@ -45,6 +45,8 @@ export default Object.freeze({
     'v8.15',
     'v8.16',
     'v8.17',
+    'v8.18',
+    'v8.19',
     'v9.0',
     'v9.1',
     'v9.2',