Add the changed values to the comment that notifies the maintainer about an improvement #9715

When someone suggests an improvement, the bot comments on the pull request and tags the maintainer. The comment does not say what changed, so the maintainer has to read the diff of the JSON file.

For a range change that diff is easy to misread. The events in ranges stay the same. The only line that changes is database_specific.last_known_affected_version_range, which the form deletes once the range and the fixed event agree. So the change looks like someone deleted version data. That is what happened in #9713 and #9714, where I widened the affected range of two cryptography advisories. Both the maintainer and the automated review read the diff as deleting version data.

It would help if the bot comment listed the fields that changed, with the old and the new value, for example Affected versions: >= 42.0.0, <= 48.0.0 -> >= 42.0.0, < 49.0.0.