Upgrade to API level 28

[hawkrives]

facebook/react-native#18095 (comment)

you'll need to add android:usesCleartextTraffic="true" to your AndroidManifest.xml file.

This is only necessary for debug/development builds; please don't do this for release builds. Use manifest placeholders to set this appropriately for each build type.

[hawkrives]

A later comment added this:

---

If anyone is upgrading to SDK 28, you'll need to add

android:usesCleartextTraffic="${isDebug}"

to the <application> element in your AndroidManifest.xml file, and

    buildTypes {
        debug {
            manifestPlaceholders = [isDebug:true]
        }

        release {
            manifestPlaceholders = [isDebug:false]
        }
    }

to your app/build.gradle file