Set signingConfig for release build type

This allows to install the app in `release` build type on devices

Author: wzieba

build-logic/convention/src/main/kotlin/GravatarAndroidApplicationConventionPlugin.kt

@@ -46,6 +46,7 @@ class GravatarAndroidApplicationConventionPlugin : Plugin<Project> {
                     getDefaultProguardFile("proguard-android-optimize.txt"),
                     "proguard-rules.pro",
                 )
+                signingConfig = signingConfigs.getByName("debug")
             }
         }
     }