add test for myjdownloader credentials/config

tests/credentials-test/goss.yaml

@@ -0,0 +1,11 @@
+file:
+  /opt/JDownloader/cfg/org.jdownloader.api.myjdownloader.MyJDownloaderSettings.json:
+    exists: true
+    mode:
+      or:
+      - "0664"
+      - "0644"
+    filetype: file
+    contains:
+      - mymail@example.com
+      - mypassword

tests/default/goss.yaml

@@ -30,6 +30,8 @@ file:
 package:
   ffmpeg:
     installed: true
+  jq:
+    installed: true
 user:
   jdownloader:
     exists: true