Update README.md

Author: atdrendel

README.md

@@ -1,3 +1,49 @@
 # JSON
 
-A description of this package.
+JSON is a simple, type-safe JSON type implemented in pure Swift. It's intended to be lightweight and ergonomic. Most especially, it can be used in model value types that need to be sendable.
+
+## Usage
+
+```swift
+let json: JSON = [
+    "one": 2,
+    "two_text": "two",
+    "pi": 3.14,
+    "yes": true,
+    "null": nil,
+    "object": [
+        "three": 3,
+        "four_text": "four",
+        "null": nil,
+        "inner_array": [
+            "index_0",
+            false,
+            4.20,
+        ] as [Any?],
+    ] as [String: Any?],
+]
+
+json["one"].integerValue // 2
+json["object"]["four_text"].stringValue // "four"
+```
+
+## Installation
+
+### Swift Package Manager
+
+To use JSON with the Swift Package Manager, add a dependency to your `Package.swift` file:
+ 
+ ```swift
+ let package = Package(
+    dependencies: [
+        .package(
+            url: "https://github.com/shareup/json-apple.git", 
+            from: "1.0.0"
+        )
+    ]
+ )
+```
+
+## License
+
+The license for JSON is the standard MIT licence. You can find it in the `LICENSE` file.