* added duplicate manga check
When adding a manga to your library, the app will go through each manga previously added and compare their names. If a match is detected, it will prompt the user and ask for confirmation. On this prompt there is also an option to view the other manga.
* added german translations for newly added strings
* Revert "added german translations for newly added strings"
This reverts commit 71ada620671651daeeb2546aecd02400a4bc86bc.
* changed `AlertDialog.Builder` to `MaterialAlertDialogBuilder`
* using SQL query instead of filtering entire library with Kotlin
(cherry picked from commit 71ddb1657440d54178f10fd62e3d0c66ee95a5a0)