[wrt][WEBQA-154] Add a file .gitkeep

- Build apk successfully, no error

Impacted TCs num(approved): New 0, Update 1, Delete 0
Unit test Platform: Android
Android test result summary: Pass 1, Fail 0, Block 0
Merge pull request #1016 from wanghongjuan/wanghongjuan/wrt/WEBQA-154

[wrt][WEBQA-154] Add a file .gitkeep