Add Kotlin support

build.gradle

@@ -1,18 +1,20 @@
 buildscript {
+    ext.kotlin_version = '1.5.21'
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.0.0-beta04'
-        classpath 'com.google.gms:google-services:4.3.4'
-        classpath 'com.google.firebase:firebase-crashlytics-gradle:2.5.2'
+        classpath 'com.android.tools.build:gradle:7.0.0-beta05'
+        classpath 'com.google.gms:google-services:4.3.8'
+        classpath 'com.google.firebase:firebase-crashlytics-gradle:2.7.1'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
 
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }