ICU-22677 update licensing

- add SPDX link in LICENSE
- update date in README.md
- unicode-org/.github#15

LICENSE

@@ -2,7 +2,7 @@ UNICODE LICENSE V3
 
 COPYRIGHT AND PERMISSION NOTICE
 
-Copyright © 2016-2023 Unicode, Inc.
+Copyright © 2016-2024 Unicode, Inc.
 
 NOTICE TO USER: Carefully read the following legal agreement. BY
 DOWNLOADING, INSTALLING, COPYING OR OTHERWISE USING DATA FILES, AND/OR
@@ -38,6 +38,8 @@ not be used in advertising or otherwise to promote the sale, use or other
 dealings in these Data Files or Software without prior written
 authorization of the copyright holder.
 
+SPDX-License-Identifier: Unicode-3.0
+
 ---------------------
 
 Third-Party Software Licenses

README.md

@@ -26,7 +26,7 @@
 
 ### Copyright & Licenses
 
-Copyright © 2016-2023 Unicode, Inc. Unicode and the Unicode Logo are registered trademarks of Unicode, Inc. in the United States and other countries.
+Copyright © 2016-2024 Unicode, Inc. Unicode and the Unicode Logo are registered trademarks of Unicode, Inc. in the United States and other countries.
 
 The project is released under [LICENSE](./LICENSE).