Track the progress of the implementation of the `reason` modifier

https://github.com/uBlockOrigin/uBlock-issues/issues/1195#event-17872322872 + https://github.com/uBlockOrigin/uBlock-issues/issues/1195#issuecomment-2922182584

It would be useful to implement e.g. trim when AdGuard do not want such a description per rule from the Filter creator in AdGuard and the Filter creator did not generate two Filters or split them by the `!#include` mechanism in one master file.

Optionally, AdGurd can try to label it as an alias `_` modifier with a value with any text.