Abstract Key-Value Database Class

abstract-level provides an abstract interface for building lexicographically sorted key-value databases, serving as the foundation for the entire LevelDB ecosystem in JavaScript/TypeScript. It defines the core API, including operations like `put`, `get`, `del`, `batch`, and iterators, along with support for encodings, sublevels, events, and hooks. The current stable version is `3.1.1`, with active development reflected in regular minor and patch releases, and major versions introducing significant breaking changes (e.g., v2 to v3). Its key differentiator is being a specification rather than an implementation, allowing concrete database modules like `level` or `classic-level` to adhere to a common, well-defined API. It ships with comprehensive TypeScript types and leverages modern JavaScript features.