chore: add license (#25)

Author: ShookLyngs

LICENSE

@@ -0,0 +1,15 @@
+ISC License
+
+Copyright (c) 2024 CELL Studio
+
+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+PERFORMANCE OF THIS SOFTWARE.

README.md

@@ -4,3 +4,7 @@
 
 - [@rgbpp-sdk/btc](./packages/btc): Bitcoin part of the SDK
 - [@rgbpp-sdk/ckb](./packages/ckb): Nervos CKB part of the SDK
+
+## License
+
+[ISC](./LICENSE) License