Update license files.

[xStrom]

This is to ensure that they will be part of the published package. Technically they are symlinks to the repo root, to save space.

[DJMcNab]

I don't really like adding in symlinks, because they can potentially cause pain, and we're so unlikely to ever change the contents of these files (e.g. it doesn't increase the size of the repository, only the size of any clone, since it uses the same data as the root files)

That being said, symlinks is what wgpu uses (gfx-rs/wgpu#2604), so this is probably a fine option - especially if we do ever update the licenses.
Although that seems to just have been cargo-culted from tokio-rs/prost#619. The paper trail of reasoning breaks down there

In tokio-rs/tracing#842, they decided on just copying the files, because of similar concerns about windows.

Overall, I think I prefer copying the files, but can accept either approach

[xStrom]

Druid uses symbolic links and has a section about making sure they're enabled on Windows. This is a significant issue only for people who publish packages, so it's not too difficult to have this documented as part of a general Linebender publishing guide. Also as it stands now I think I might be the only Linebender publisher who actually publishes on Windows.

Although yeah even others who don't have symlinks enabled may find it tricky to open the files.

[nicoburns]

IMO needing special instructions for windows is reason e ough not to use symlinks. I reckon we should just duplicate the file. These files are tiny anyway.

[xStrom]

Alright I removed the symlinks and went with standard files.