Add licensing data for https://reuse.software/

[FedericoCeratto]

This could be used to later remove img/README.md and simplify license management using reuse lint in CI
Please review the licensing data before merging.
The project can then be registered at https://api.reuse.software/register to obtain a badge similar to https://api.reuse.software/info/codeberg.org/FedericoCeratto/rrdnsd

[ubruhin]

Thanks for working on this @FedericoCeratto! 🎉

I didn't review the dep5 file yet in detail, but I totally agree it makes sense to replace the img/README.md by a structured format.

What bothers my a little bit is to add all the license files which are kind of unnecessary duplication since they are easily available in the internet (they could probably even be automatically downloaded on demand by a tool) 🙈 Luckily there are not too many files, but still generally I like to keep the repository as clean as possible. But I know it's not your decision as it is specified by REUSE. Maybe @dbrgn has any opinion about that?

In any way, I'll try to review the dep5 soon. I also opened LibrePCB/docker-librepcb-dev#34 to keep in mind adding reuse lint to our CI Docker images.

[ubruhin]

I have now removed the Files: * entry because it would wrongly apply a license to any file we forgot to list. And now CI fails (of course) because of some very old icons we don't know the license of:

* img/actions/add_component.png
* img/actions/export_gerber.png
* img/actions/export_zip.png
* img/actions/new_folder.png
* img/actions/select.png
* img/library/3d_model.png
* img/library/component.png
* img/library/device.png
* img/places/file.png
* img/places/folder.png
* img/places/folder_open.png
* img/status/info.png

So I think we have to replace these icons first before we can get this PR merged.

[FedericoCeratto]

@ubruhin I suggest rebasing this PR on top of #1336 - I haven't done it because you force-pushed some commits and I don't want to mess up you local git checkout

[ubruhin]

@FedericoCeratto I think it makes more sense the other way around, i.e. getting this PR ready first, then updating #1336. This is almost done as I have replaced some icons with unknown license, now only a few ones are left:

* img/actions/new_folder.png
* img/actions/select.png
* img/library/3d_model.png
* img/library/device.png
* img/places/folder.png
* img/places/folder_open.png

[ubruhin]

Found the source of these icons, now all licenses are clarified and reuse lint succeeds on CI!

If there are no objections, I'll merge this soon.

[FedericoCeratto]

@ubruhin OK!