docs: Add license section

Author: jcs090218

README.md

@@ -24,6 +24,23 @@ to install the language server! 🎉
 | `ellsp.start` | Start the `shader langauge server` |
 | `ellsp.stop`  | Stop the `shader langauge server`  |
 
+## ⚜️ License
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+See [`LICENSE`](./LICENSE) for details.
+
 
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