docs(libanki): README.md

libanki/README.md

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+# `:libanki`
+
+A 1:1 port of Anki's [`pylib`](https://github.com/ankitects/anki/tree/main/pylib), defining core domain types and wrapping the Rust backend.
+
+## Aims
+
+`:libanki` aims to mirror upstream `pylib`, so it is easy to bring across any future changes.
+
+One of the following annotations should be used on all new public code:
+
+- Use [`@LibAnkiAlias`](src/main/java/com/ichi2/anki/libanki/utils/LibAnkiAlias.kt) to indicate which upstream method is replicated. The implementation should follow the upstream implementation as close as possible, discrepancies should be described in the documentation.
+  - Kotlin uses `camelCase`, Python uses `snake_case`, this allows for easy mapping
+- Use [`@NotInPyLib`](src/main/java/com/ichi2/anki/libanki/utils/NotInPyLib.kt) for AnkiDroid-specific additions with no `pylib` equivalent.
+  - Functionality needs **strong** justification as to why it can't exist in `:anki-common` 
+  (if shared between features), a feature module, or `:AnkiDroid`.
+
+## See also
+
+- [`anki:pylib`](https://github.com/ankitects/anki/tree/main/pylib) - where this code is ported from.
+- [`anki:proto`](https://github.com/ankitects/anki/tree/main/proto) - function definitions, exposed
+ via `.backend` (`net.ankiweb.rsdroid.Backend`).
+- [`anki:rslib`](https://github.com/ankitects/anki/tree/main/rslib) - the implementation of the functions (Rust-based).
+- [Anki-Android-Backend](https://github.com/ankidroid/Anki-Android-Backend/) - packages the Rust backend (`rsdroid`); generates Kotlin code 
+  from types in `anki:proto` and defines an Android-based database abstraction.
+