docs: update README and roadmap for v0.3.0 release

- Update feature list with all Phase 1-3 capabilities
- Add async support, serialization, and performance highlights
- Update bundle size to 5 kB
- Bump version references to v0.3.0
- Reflect completed phases in roadmap

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ackermannQ

README.md

@@ -34,14 +34,17 @@ if (!res.ok) {
 
 - **🎯 Exhaustive matching** - TypeScript enforces that you handle all error types
 - **🔧 Ergonomic API** - Declarative `matchError` / `matchErrorOf` chains with:
+  - `.map()` for error transformation
   - `.select()` for property extraction
   - `.withAny()` for matching multiple types
   - `.withNot()` for negation patterns
   - `.when()` for predicate matching
-- **📦 Tiny & fast** - ~2 kB, zero dependencies, works everywhere
+- **📦 Tiny & fast** - ~5 kB, zero dependencies, O(1) tag-based matching
 - **🛡️ Type-safe** - Full TypeScript support with strict type checking
 - **🔄 Result pattern** - Convert throwing functions to `Result<T, E>` types
-- **🔨 Composable guards** - Reusable type guards with `isErrorOf()`
+- **🔨 Composable guards** - Reusable type guards with `isErrorOf()`, `isAnyOf()`, `isAllOf()`
+- **⚡ Async support** - Native async/await with `matchErrorAsync()` and `matchErrorOfAsync()`
+- **💾 Serialization** - JSON serialization with `serialize()`, `deserialize()`, `toJSON()`, `fromJSON()`
 
 ## 🚀 Quick Start
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ts-typed-errors",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "Exhaustive error matching utilities for TypeScript (defineError, matchError, matchErrorOf, wrap)",
   "type": "module",
   "sideEffects": false,

roadmap.md

@@ -473,5 +473,5 @@ This roadmap is subject to change based on:
 - Performance considerations
 
 **Last updated:** October 16, 2025
-**Current version:** v0.0.6
+**Current version:** v0.3.0