fix: correct phpstan errors and update schema urls
This commit includes several modifications:
- Removed the ignoreErrors directives in phpstan-baseline.neon as the corresponding issues have been resolved
- Updated 'itemtype' URL from 'http://' to 'https://'
- Removed an obsolete comment block above the getSite method in Timeline.php
- Added variable documentation in types/timeline.php to clarify variable types and avoid phpstan errors.
Related: #3 (closed)