OpenCC resource repository: per-file upstream licenses

No blanket model license is granted by this repository. Each model and native
resource remains subject to its applicable upstream license and notices. Format
conversion, quantization, compression or packaging does not replace those terms.
An artifact's publication metadata and accompanying notices must identify its
source and applicable terms before it is offered as a production resource.

This initial repository metadata does not contain model weights and does not
assert that resource publication or application integration is complete.