Crawl for releases in more places

Currently we only look in GitHub releases to find releases of a package, but not all use it.

e.g. https://github.com/getadaptly/changelog-generator/pull/11

Sometimes they are just pointing to external website: https://github.com/pallets/jinja/releases

Or this: https://github.com/pandas-dev/pandas/releases/tag/v2.0.3