Add FAQ entry for configuring SOURCE_DATE_EPOCH

[loosebazooka]

This can maybe configured by the user with timestamp settings.

we might need to provide support for milliseconds.

https://reproducible-builds.org/specs/source-date-epoch/

[chanseokoh]

Reading this again, it's not clear what we intended. Is it an FAQ explaining how to make Maven or other tools generate files with a desired timestamp without changing the local machine time? Or is it that Jib should also honor SOURCE_DATE_EPOCH? If so, for the image creation time or files in an image?

[alicejli]

Closing as there has not been any feedback on this request for several years and it's unclear what the desired outcome is.