add README.md

Author: abdel-17

README.md

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+# Swift Rational
+
+## Introduction
+
+Swift Numerics provides the `RationalModule` module for working with rational numbers in Swift.
+```swift
+import RationalModule
+
+let half = Rational<Int>(1, 2)
+```
+
+`RationalModule` has only a single dependency, [swift-numerics](https://github.com/apple/swift-numerics/tree/main).
+
+## Using Swift Rational in your project
+
+To use Swift Rational in a SwiftPM project:
+
+1. Add the following line to the dependencies in your `Package.swift` file:
+
+```swift
+.package(url: "https://github.com/abdel-17/swift-rational", from: "1.0.0")
+```
+
+2. Add `RationalModule` as a dependency for your target:
+
+```swift
+.target(
+	name: "TargetName",
+	dependencies: [
+		.product(name: "RationalModule", package: "swift-rational")
+	]
+)
+```
+
+3. Add `import RationalModule` in your source code.
+
+## API
+
+`RationalModule` exports the `Rational` struct. It conforms to standard Swift protocols like `AdditiveArithmetic`, `Numeric`, `Hashable`, `Comparable`, and more.
+
+You can create a `Rational` value using the fraction initializer.
+```swift
+let half = Rational(2, 4)
+print(x.numerator)		// 1
+print(x.denominator)	// 2
+```
+
+You can also use the integer initializer.
+```swift
+let one = Rational(1)
+```
+
+Or simply an integer literal.
+```swift
+let two: Rational<Int> = 2
+```
+
+`Rational` supports the standard arithmetic and comparison operators.
+```swift
+Rational(1, 2) + Rational(1, 4)		// Rational(3, 4)
+Rational(1)    - Rational(1, 2)		// Rational(1, 2)
+Rational(2)    * Rational(3, 4)		// Rational(3, 2)
+Rational(1)    / Rational(1, 2)		// Rational(2, 1)
+Rational(1, 2) < Rational(3, 4)		// true
+```