Added callback for postprocessing the GUIDs list

[ZimM-LostPolygon]

No description provided.

[lilyvelour]

Thanks for the PR! Just one minor change needed for backwards compatibility.

If I may ask, what use case did you have in mind for this callback?

[ZimM-LostPolygon]

My use case:
The SDK project has some folders like:

Assets/MySdk/
Assets/MySdkTests/
Assets/MySdkBuildScripts/
Assets/MySdkThirdPartyIntegrations/

This is convenient for working with the project, but with the normal Asset Store upload process, it would mean that all these folders will be uploaded, whereas I only want to upload the contents of Assets/MySDK/ folder. This callback allows me to filter out files that I don't want to be included in the Asset Store package.

Actually, I've been using it like that for a few years, and just realized I hadn't done the PR :)

[ZimM-LostPolygon]

@lmontoute Updated my branch. Can this be merged now, perhaps? Calling from command line is not an issue, guidListPostprocessCallback will just be null.

[lilyvelour]

The code here has my approval but one minor change is needed. Some lines seem to have been converted to tabs (and some changed as well), which will break our internal linter — can we revert the unnecessary format changes and ensure the added lines are formatted correctly?

[lilyvelour]

Are there any actual changes in this block?