How to copy `string.xml` to capacitor-cordova-android-plugins?

I set some variable string needed for my cordva library in my android project string.xml,
but error comes in gradle task :capacitor-android:verifyReleaseResources, cannot finding the variable.
Because of this error I cannot build with AppFlow. (Just running locally with Android Studio is working.)

For exmaple, the name of the variable needed called KAKAO_APP_KEY.
After cap sync android, in capacitor-cordova-android-plugins's AndroidManifest.xml, there is the code:

<meta-data android:name="com.kakao.sdk.AppKey" android:value="@string/kakao_app_key"/>

and in the app folder’s string.xml, there is kakao_app_key:

<string name="kakao_app_key">foo</string>

But because there is NO strings.xml in capacitor-cordova-android-plugins folder, there is error.
So I want to copy strings.xml file to capacitor-cordova-android-plugins folder with cap sync android.

Please let me give some idea how to do this.

Thank you.