docs(readme): add Unsplash license; link to ours

README.md

@@ -132,7 +132,7 @@ What differentiates HiColor is being a small dedicated tool and embeddable C lib
 
 ## License
 
-MIT.
+[MIT](LICENSE).
 
 [cute\_png](https://github.com/RandyGaul/cute_headers/) is copyright (c) 2019, 2021-2023 Randy Gaul and is licensed under the zlib license.
 
@@ -141,3 +141,7 @@ MIT.
 [Building photo with a plane from Bordeaux](https://unsplash.com/photos/AwtncJT1qKs) (`bordeaux-15bit.png`) by olaf wisser.
 
 [Portland photo](https://unsplash.com/photos/PWBXQJ7PUkI) (`tests/photo.png`) by Orlova Maria.
+
+License:
+
+> Unsplash grants you an irrevocable, nonexclusive, worldwide copyright license to download, copy, modify, distribute, perform, and use photos from Unsplash for free, including for commercial purposes, without permission from or attributing the photographer or Unsplash. This license does not include the right to compile photos from Unsplash to replicate a similar or competing service.