license added in default generated test file

apps/remix-ide/src/app/tabs/testTab/testTab.js

@@ -62,7 +62,9 @@ class TestTabLogic {
     let relative = remixPath.relative(this.currentPath, remixPath.dirname(fileToImport))
     if (relative === '') relative = '.'
     const comment = hasCurrent ? `import "${relative}/${remixPath.basename(fileToImport)}";` : '// Import here the file to test.'
-    return `pragma solidity >=0.4.22 <0.8.0;
+    return `// SPDX-License-Identifier: GPL-3.0
+    
+pragma solidity >=0.4.22 <0.8.0;
 import "remix_tests.sol"; // this import is automatically injected by Remix.
 import "remix_accounts.sol";
 ${comment}