Add a way to add files after exporting all files in an EditorExportPlugin

[Daylily-Zeleen]

Describe the project you are working on

A custom build godot engine.

Describe the problem or limitation you are having in your project

I can do some postprocess and add a description fils in the packed file, because of the EditorExportPlugin has not a way to add file after exporting all files.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

If it is impolemented, I can collect every exported file in _export_file(), then do some postprocess to dump a description file and add it into the packed file after exporting files finished.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

1. Add a virtual method _export_files_end() for EditorExportPlugin.
2. Let it be called after the step of exporting files finished in EditorExportPlatform::export_project_files().
3. Then add extra files like the step of exporting files( besides add as a remap file).

Here is my implemention 73276.

If this enhancement will not be used often, can it be worked around with a few lines of script?

The export workflow is in the core code, we can't change it in script.

Is there a reason why this should be core and not an add-on in the asset library?

The same as above.

[KoBeWi]

Isn't it the same as _export_end() method? It can be used to copy some files (albeit you need to do it manually)

[Daylily-Zeleen]

Isn't it the same as _export_end() method? It can be used to copy some files (albeit you need to do it manually)

_export_end() just notify user that the export workflow is finished and currently it can't be overrided in c++ directly( I let it can be overrided in c++ by this pr).

_export_end() can't add files in to the packed file( *.pck or *.zip), call add_file() in _export_end() will store file in EditorExportPlugin::extra_files without truely adding into packed file, and will be added in next time to export( the timing is just after _export_begin()).

[KoBeWi]

Ah by manually adding files I mean you can just copy them outside the PCK and they will still be loaded, but I guess a better way to do so makes sense.