Cross-platform library for working with tag storage and index

[kirillt]

For implementations on other platforms, it is good to have all data formats fixed in code shared among all implementations.

1. Separate the library into separate project, import it in the main project.
2. Convert the code of the library from Kotlin to something native.
   If possible, we should use Rust for this.

The library should manage storage parsing and saving.
It's possible to move index management into the library and achieve #142.
It's possible to move previews management into the library and achieve #115.

[kirillt]

We have the lib, it's a lot of work to move core functionality into it, but we've touched base.