Update README.md

Catherine22 · web-flow · commit 0fadd2ea6cd5 · 2019-07-30T19:24:10.000+08:00
diff --git a/README.md b/README.md
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 # AAD-Preparation
 
+![img](https://api.accredible.com/v1/frontend/credential_website_embed_image/certificate/13394960)
+
 Associate Android Developer Study Guide   
 https://developers.google.com/training/certification/associate-android-developer/study-guide/   
 
