Ignore PDF files for packages

[Bi0T1N]

This adds an entry to the .gitignore file to ignore all (new) PDF files for packages. Avoids that every single package maintainer may have it's own .gitignore file to achieve the same result... 😄

find packages/ -name .gitignore | wc -l 
154

Related to #1595 (comment)

[elegaanz]

Thank you, but unfortunately there are a few exceptions to this rule: for instance we generally allow manual files as PDF, especially if they are linked in the README. This .gitignore rule would be too generic to allow for that, and I don't think that you can refine it to allow only for some specific PDF files (judging the contents of the PDF can probably only be done by a human). I'll close for this reason.

[Bi0T1N]

Well, even if the .gitignore has a line to skip PDF files for packages you can add them to the commit by using git add --force wanted.pdf.
The other option I see to make it easier for maintainers is to allow the .gitignore file within the package directory. Currently the pipeline fails if you do so:

Error: packages/preview/iconic-salmon-svg/.gitignore: a package directory may only contain version sub-directories, not files.

The current state is that you would need to have a single .gitignore file in every version sub-directory which is cumbersome and prone to errors. And somehow useless, because you no longer touch the version directory after the merge to the main branch.

[Bi0T1N]

Should I create an issue for this if further discussion is needed?

[elegaanz]

Yes please, it will be more visible than this PR.