fixed up yaml

README.md

@@ -1,10 +1,10 @@
 ---
 language: 
   - eng
-thumbnail: "url to a thumbnail used in social sharing"
+thumbnail: "https://townsquare.media/site/88/files/2020/06/C_Charlotte_RGB_7484.jpg"
 tags:
 - dialogue
-license: "any valid license identifier"
+license: afl-3.0
 datasets:
 - schema guided dialogue
 metrics: