簽名配置錯誤：Could not get unknown property~~.md

錯誤：

Could not get unknown property 'ys' for SigningConfig container of type org.gradle.api.internal.FactoryNamedDomainObjectContainer.

解決：
signingConfigs{}模塊寫在buildTypes{}上層，要比buildTypes{}先執行，不然去哪裏找簽名。