add license defintion to composer.json

composer.json

@@ -1,12 +1,12 @@
 {
     "name": "d3/linkmobility-php-client",
     "type": "library",
-    "description": "PHP client for Linkmobility API (de)",
+    "description": "PHP client for LINK Mobility Austria API",
     "keywords": [
-        "linkmobility",
+        "LINK Mobility",
         "php",
         "sms",
-        "sms gateway"
+        "message gateway"
     ],
     "homepage": "https://d3data.de/",
     "authors": [
@@ -17,6 +17,9 @@
         "role": "Owner"
       }
     ],
+    "license": [
+      "GPL-3.0-or-later"
+    ],
     "require": {
         "php": "^7.0",
         "beberlei/assert": "^2.9.9",