Add namespace support and enhance WASM API

v0.3.0 - no_std + Embedded Support

Major Features

• no_std support with alloc for embedded systems
• BTreeMap backend for no_std environments
• WASM compatibility for browser applications
• Triple configuration support: std/no_std+nanoserde/pure-no_std

New APIs

• TinyKV::new() - In-memory store (no_std compatible)
• from_data() - Create from serialized data
• to_data() - Serialize to string

Breaking Changes

None! Fully backward compatible.

Usage

# Default (std + serde)
tinykv = "0.3"

# Embedded (no_std + nanoserde)  
tinykv = { version = "0.3", default-features = false, features = ["nanoserde"] }

# Ultra-minimal (pure no_std)
tinykv = { version = "0.3", default-features = false }

v0.2.0 - nanoserde Support

New Features

• Added nanoserde support via feature flag for minimal builds
• Smaller binary size and faster compilation with nanoserde backend
• Backward compatible - existing code works unchanged

Usage

• Default: tinykv = "0.2" (uses serde)
• Minimal: tinykv = { version = "0.2", default-features = false, features = ["nanoserde"] }

Thanks to Beautiful_Lilly21 for the suggestion!