Support IPv6 including fast fallback to IPv4

See https://square.github.io/okhttp/changelogs/changelog/#version-500-alpha4

src/main/kotlin/com/looker/droidify/network/Downloader.kt

@@ -32,6 +32,7 @@ object Downloader {
 
     private fun createClient(proxy: Proxy?, cache: Cache?): OkHttpClient {
         return OkHttpClient.Builder()
+            .fastFallback(true)
             .connectTimeout(30L, TimeUnit.SECONDS)
             .readTimeout(15L, TimeUnit.SECONDS)
             .writeTimeout(15L, TimeUnit.SECONDS)

src/main/kotlin/com/looker/droidify/network/DownloaderX.kt

@@ -50,6 +50,7 @@ object DownloaderX {
             clients[clientConfiguration] ?: run {
                 val client = this.client
                     .newBuilder()
+                    .fastFallback(true)
                     .connectTimeout(30L, SECONDS)
                     .readTimeout(15L, SECONDS)
                     .writeTimeout(15L, SECONDS)