Add proper documentation & link to in README rather than all-in-one README

Sources/ErrorKit/ErrorKit.docc/ErrorKit.md

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+# ``ErrorKit``
+
+Making error handling in Swift more intuitive and powerful with clearer messages, type safety, and user-friendly diagnostics.
+
+@Metadata {
+   @PageImage(purpose: icon, source: "ErrorKit")
+}
+
+## Overview
+
+Swift's error handling has several limitations that make it challenging to create robust, user-friendly applications:
+- The `Error` protocol's confusing behavior with `localizedDescription`
+- Hard-to-understand system error messages
+- Limited type safety in error propagation
+- Difficulties with error chain debugging
+- Challenges in collecting meaningful feedback from users
+
+ErrorKit addresses these challenges with a suite of lightweight, interconnected features you can adopt progressively.
+
+## Core Features
+
+These foundational features improve how you define and present errors:
+
+@Links(visualStyle: detailedGrid) {
+   - <doc:Throwable-Protocol>
+   - <doc:Enhanced-Error-Descriptions>
+}
+
+## Swift 6 Typed Throws Support
+
+Swift 6 introduces typed throws (`throws(ErrorType)`), bringing compile-time type checking to error handling. ErrorKit makes this powerful feature practical with solutions for its biggest challenges:
+
+@Links(visualStyle: detailedGrid) {
+   - <doc:Typed-Throws-and-Error-Nesting>
+   - <doc:Error-Chain-Debugging>
+}
+
+## Ready-to-Use Tools
+
+These practical tools help you implement robust error handling with minimal effort:
+
+@Links(visualStyle: detailedGrid) {
+   - <doc:Built-in-Error-Types>
+   - <doc:User-Feedback-with-Logs>
+}
+
+## How These Features Work Together
+
+ErrorKit's features are designed to complement each other while remaining independently useful:
+
+1. **Start with improved error definitions** using `Throwable` for custom errors and `userFriendlyMessage(for:)` for system errors.
+
+2. **Add type safety with Swift 6 typed throws**, using the `Catching` protocol to solve nested error challenges. This pairs with error chain debugging to understand error flows through your app.
+
+3. **Save time with ready-made tools**: built-in error types for common scenarios and simple log collection for user feedback.
+
+Each feature builds upon the foundations laid by the previous ones, but you can adopt any part independently based on your needs.
+
+## Adoption Path
+
+Here's a practical adoption strategy:
+
+1. Replace `Error` with `Throwable` in your custom error types
+2. Use `ErrorKit.userFriendlyMessage(for:)` when showing system errors
+3. Adopt built-in error types where they fit your needs
+4. Implement typed throws with `Catching` for more robust error flows
+5. Add error chain debugging to improve error visibility
+6. Integrate log collection with your feedback system