Add license headers

index.js

@@ -1,3 +1,7 @@
+// babel-plugin-react-translate
+// (c) Vitaliy Filippov 2021+
+// SPDX-License-Identifier: LGPL-3.0
+
 const fs = require('fs');
 
 module.exports = function(babel)

plural_ru.js

@@ -1,3 +1,7 @@
+// babel-plugin-react-translate
+// (c) Vitaliy Filippov 2021+
+// SPDX-License-Identifier: LGPL-3.0
+
 export default function plural_ru(count, one, few, many)
 {
     var sto = count % 100;

runtime.js

@@ -1,3 +1,7 @@
+// babel-plugin-react-translate
+// (c) Vitaliy Filippov 2021+
+// SPDX-License-Identifier: LGPL-3.0
+
 import plural from './plural_ru.js';
 
 const strings = {};