[ImgBot] Optimize images

*Total -- 83.92kb -> 46.79kb (44.25%)

/assets/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/mipmap-mdpi/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/mipmap-xxhdpi/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/mipmap-hdpi/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/mipmap-xhdpi/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/mipmap-xxxhdpi/achieve.png -- 12.48kb -> 6.45kb (48.33%)
/android/app/src/main/res/drawable/background.jpg -- 9.02kb -> 8.08kb (10.36%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp