Add README FAQ and align license headers

protocol/tagtinker_proto.c

@@ -6,7 +6,7 @@
  * 2. Pack pixels into the tag's raw or RLE bitmap format.
  * 3. Wrap those bytes into the IR frames that the tag understands.
  *
- * SPDX-License-Identifier: MIT
+ * SPDX-License-Identifier: GPL-3.0-only
  */
 
 #include "tagtinker_proto.h"

protocol/tagtinker_proto.h

@@ -4,7 +4,7 @@
  * This layer turns barcodes, pixels, and payload bytes into the frames
  * that the Flipper sends over IR to the tag.
  *
- * SPDX-License-Identifier: MIT
+ * SPDX-License-Identifier: GPL-3.0-only
  */
 
 #pragma once