docs: Add license section to README

Author: ZZHow1024

README.md

@@ -18,6 +18,10 @@ https://github.com/ZZHow1024/MagicEncoding/releases
 
 ---
 
+## License
+
+This project is licensed under the GNU General Public License v3.0 - see the [LICENSE](LICENSE) file for details.
+
 ## **Instructions for use**
 
 - Determine the operating system you are using.

README_ZH.md

@@ -18,6 +18,10 @@ https://github.com/ZZHow1024/MagicEncoding/releases
 
 ---
 
+## License
+
+This project is licensed under the GNU General Public License v3.0 - see the [LICENSE](LICENSE) file for details.
+
 ## 使用说明
 
 - 确定您使用的操作系统。