add license file

Signed-off-by: Jiaqi Gao <[email protected]>

Author: gaojiaqi7

LICENSE.md

@@ -0,0 +1,12 @@
+This project uses BSD-2-Clause-Patent license.
+
+[SPDX-License-Identifier](https://spdx.org/licenses/): [BSD-2-Clause-Patent](https://spdx.org/licenses/BSD-2-Clause-Patent.html).
+
+```
+Copyright (c) 2022-2024, Intel Corporation.  All rights reserved.
+
+SPDX-License-Identifier: BSD-2-Clause-Patent
+```
+
+Some of the files are derived from [td-shim](https://github.com/confidential-containers/td-shim) project.
+They reuse [td-shim license](https://github.com/confidential-containers/td-shim/blob/main/LICENSE) - [BSD-2-Clause-Patent](https://spdx.org/licenses/BSD-2-Clause-Patent.html).