chore(license): update to LICENSE v3

- unicode-org/.github#6

README.md

@@ -8,7 +8,7 @@
 
 Evidence images for both IRG N2107R2 and IRG N2232R are easily downloaded from the [Latest Release](https://github.com/unicode-org/uk-source-ideographs/releases/latest/) as *UKSourceEvidence.pdf*, which is a 1,236-page bookmarked PDF.
 
-The representative glyphs that correspond to the UK-source ideographs are available in TrueType (TTF) format, their use is covered under the terms of the [Arphic Public License](https://ftp.gnu.org/gnu/non-gnu/chinese-fonts-truetype/LICENSE) (also see *LICENSE.md*), and can be easily downloaded from the [Latest Release](https://github.com/unicode-org/uk-source-ideographs/releases/latest/). The representative glyphs are mapped from PUA (*Private Use Area*) code points as specified in the Excel file that is attached to each PDF.
+The representative glyphs that correspond to the UK-source ideographs are available in TrueType (TTF) format, their use is covered under the terms of the [Arphic Public License](https://ftp.gnu.org/gnu/non-gnu/chinese-fonts-truetype/LICENSE) (also see *[LICENSE](./LICENSE)*), and can be easily downloaded from the [Latest Release](https://github.com/unicode-org/uk-source-ideographs/releases/latest/). The representative glyphs are mapped from PUA (*Private Use Area*) code points as specified in the Excel file that is attached to each PDF.
 
 The table below indicates the number of UK-source ideographs that have been encoded in CJK Unified Ideographs **Extension** blocks, either from IRG working sets or as horizontal extensions, and as of [Unicode Version 15.0](https://www.unicode.org/versions/Unicode15.0.0/):
 
@@ -23,3 +23,12 @@ The table below indicates the number of UK-source ideographs that have been enco
 [H](https://unicode.org/charts/PDF/U31350.pdf) | 917 | IRG Working Set 2017
 
 UK submissions to future IRG working sets will be added to this repository as appropriate.
+
+### Copyright & Licenses
+
+Copyright © 2020-2023 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).
+
+A CLA is required to contribute to this project - please refer to the [CONTRIBUTING.md](https://github.com/unicode-org/.github/blob/main/.github/CONTRIBUTING.md) file (or start a Pull Request) for more information.
+