Reduce noise in composer package download

[pierotibou]

Description

Update .gitattributes file to reduce the number of files and folder that are packaged when using composer.

Fixes #2181

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[realFlowControl]

AFAIK this only affects composer, so we might also export-ignore the profiler directory and maybe even the ext directory? WDYT?

[PROFeNoM]

maybe even the ext directory?

Are we sure we're not removing stuff that might be used by someone (e.g., the stub files)

[pierotibou]

WDYT?

Thanks @realFlowControl. I'm not entirely sure that's why I asked for 👀 . If we have any doubt I'd rather stay on the conservative side of things.

[bwoebi]

More precisely export-ignore affects what's downloaded when downloading the repository as a .tar.gz file directly from github via the built-in functionality.

And then affects composer indirectly through that. But given that it's broader than just composer, essentials to building the extensions should still stay.

[bwoebi]

I would also add tests there.

[pierotibou]

I would also add tests there.

@bwoebi, indeed they are already in the original file

[bwoebi]

Oh, it's not a new file, just added to it. Sorry :-)