Added SPDX identifier.

2018-08-01 16:25:42 +02:00 · 2018-08-01 16:25:42 +02:00 · e888cca2b7
--- a/README.md
+++ b/README.md
@ -55,3 +55,5 @@ distributed together with all the following files:
   README
 ```
 If you receive only some of these files from someone, complain!
+
+SPDX-License-Identifier: LPPL-1.3c+