add back mockup image license entries, see #19

Author: jessegreenberg

images/license.json

@@ -54,5 +54,29 @@
     "projectURL": "http://phet.colorado.edu",
     "license": "contact [email protected]",
     "notes": ""
+  },
+  "model-screen-mockup.png": {
+    "text": [
+      "Copyright 2021 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Amy Rouinfar, clipped from design doc"
+  },
+  "photons-screen-mockup.png": {
+    "text": [
+      "Copyright 2021 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Amy Rouinfar, clipped from design doc"
+  },
+  "waves-screen-mockup.png": {
+    "text": [
+      "Copyright 2021 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Amy Rouinfar, clipped from design doc"
   }
 }