Keychain package

* Added the Keychain package
* Added a Makefile to easily build the package
* Updated the README with additional information

README.md

@@ -1,3 +1,39 @@
 # Keychain
 
-A Swift package for the Keychain
+A Swift package for interacting with the Keychain.
+
+## Requirements
+
+- macOS 12+
+- Swift 6.2+
+
+## Package Structure
+
+```
+Keychain/
+├── Package.swift
+├── Package.resolved
+└── Sources/
+    └── Keychain/
+        └── Keychain.swift
+```
+
+## Dependencies
+
+- [SwiftLintPlugins](https://github.com/SimplyDanny/SwiftLintPlugins) (≥ 0.63.2) — enforces Swift style and conventions at build time.
+
+## Usage
+
+Add the package to your `Package.swift` dependencies and import `Keychain` in your Swift files.
+
+## Makefile
+
+A `Makefile` is provided at the root of the repository to simplify common tasks.
+
+| Command        | Description                              |
+|----------------|------------------------------------------|
+| `make build`   | Builds the Swift package                 |
+| `make resolve` | Resolves package dependencies            |
+| `make clean`   | Removes build artifacts and `.swiftpm`   |
+
+Build artifacts are placed in `.build/` at the repository root (outside the package directory).