Update readme (#24)

README.md

@@ -1,8 +1,73 @@
-base62
-------
+# base62
 
-A simple base62 encoder/decoder, typically used in URL shorteners. It supports the standard [0-9A-Za-z] and alternative [0-9a-zA-Z] variants.
+A fast, zero-dependency base62 encoder/decoder library for Rust, typically used in URL shorteners. It supports both standard [0-9A-Za-z] and alternative [0-9a-zA-Z] variants.
 
 [![Build status](https://github.com/fbernier/base62/workflows/ci/badge.svg)](https://github.com/fbernier/base62/actions)
 [![Crates.io](https://img.shields.io/crates/v/base62.svg)](https://crates.io/crates/base62)
 [![Docs](https://docs.rs/base62/badge.svg)](https://docs.rs/base62)
+
+## Features
+
+- `no_std` compatible with optional `alloc` and `std` support
+- Encodes integers up to `u128`
+- Zero-copy decoding
+- Efficient string handling
+- Two encoding variants:
+  - Standard [0-9A-Za-z]
+  - Alternative [0-9a-zA-Z]
+
+## Usage
+
+Add this to your `Cargo.toml`:
+```toml
+[dependencies]
+base62 = "2"
+```
+
+### Basic Example
+
+```rust
+use base62;
+
+// Encoding
+let encoded = base62::encode(1234567890);
+assert_eq!(encoded, "1LY7VK");
+
+// Decoding
+let decoded = base62::decode("1LY7VK").unwrap();
+assert_eq!(decoded, 1234567890);
+```
+
+### No-std Usage
+
+The crate works in `no_std` environments by default:
+
+```rust
+#![no_std]
+use base62;
+
+// Encode into a fixed buffer
+let mut buf = [0u8; 22];  // Maximum size needed for u128
+let len = base62::encode_bytes(1234567890, &mut buf).unwrap();
+assert_eq!(&buf[..len], b"1LY7VK");
+
+// Decode from bytes
+let decoded = base62::decode(&buf[..len]).unwrap();
+assert_eq!(decoded, 1234567890);
+```
+
+## Feature Flags
+
+- `alloc`: Enables String allocation support (enabled by default)
+- `std`: Enables std::io traits support
+
+## Performance
+
+The library is optimized for both encoding and decoding performance:
+- Zero-copy decoding
+- Efficient buffer management
+- Direct string manipulation for optimal performance when appending
+
+## License
+
+Licensed under the MIT license. See LICENSE for details.