This adds SPDX license headers to all source code files, following the
REUSE[1] specification. This does not include any asset files (such as
generated JSON files, or textures). While REUSE does support doing so
with ".license" files, for now we define these licences using the
.reuse/dep5 file.
[1]: https://reuse.software/
- Generate theme-color. Hopefully this time it works!
- Specify a site url. Technically this is wrong (we should use the
current git branch), but it's good enough for now.
- Move some options into a sub-category.