docs(android): add migrating to v15 guide

Author: dylancom

docs.json

@@ -27,7 +27,8 @@
       "Migration Guides",
       [
         ["Migrating to v5", "/migrating-to-v5"],
-        ["Migrating to v6", "/migrating-to-v6"]
+        ["Migrating to v6", "/migrating-to-v6"],
+        ["Migrating to v6", "/migrating-to-v15"]
       ]
     ]
   ]

docs/migrating-to-v15.mdx

@@ -0,0 +1,7 @@
+# Migrating to v15
+
+## Important Notice (Android Only)
+
+If you're upgrading to v15, please note that it requires Kotlin 2.0.0. Ensure your project is updated accordingly to prevent build issues.
+
+Open your `android/build.gradle` file and update the Kotlin version to "2.0.0".