Android: Convert ThemeProvider to Kotlin

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/ui/main/ThemeProvider.java

@@ -1,9 +0,0 @@
-package org.dolphinemu.dolphinemu.ui.main;
-
-public interface ThemeProvider
-{
-  /**
-   * Provides theme ID by overriding an activity's 'setTheme' method and returning that result
-   */
-  int getThemeId();
-}

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/ui/main/ThemeProvider.kt

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.dolphinemu.dolphinemu.ui.main
+
+interface ThemeProvider {
+    /**
+     * Provides theme ID by overriding an activity's 'setTheme' method and returning that result
+     */
+    val themeId: Int
+}