Add README.md

Author: somenkovnikita

README.md

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+# SPQRCode
+
+QR code detector. Simple usage, you can get recognition results via delegate or callback.
+
+- [Installation](#installation)
+    - [Swift Package Manager](#swift-package-manager)
+    - [CocoaPods](#cocoapods)
+    - [Manually](#manually)
+- [Usage](#usage)
+
+## Installation
+
+Ready for use on iOS 11+.
+
+### Swift Package Manager
+
+The [Swift Package Manager](https://swift.org/package-manager/) is a tool for automating the distribution of Swift code and is integrated into the `swift` compiler. It’s integrated with the Swift build system to automate the process of downloading, compiling, and linking dependencies.
+
+Once you have your Swift package set up, adding as a dependency is as easy as adding it to the `dependencies` value of your `Package.swift`.
+
+```swift
+dependencies: [
+    .package(url: "https://github.com/sparrowcode/SPQRCode", .upToNextMajor(from: "1.0.0"))
+]
+```
+
+### CocoaPods:
+
+[CocoaPods](https://cocoapods.org) is a dependency manager. For usage and installation instructions, visit their website. To integrate using CocoaPods, specify it in your `Podfile`:
+
+```ruby
+pod 'SPQRCode'
+```
+
+### Manually
+
+If you prefer not to use any of dependency managers, you can integrate manually. Put `Sources/SPSafeSymbols` folder in your Xcode project. Make sure to enable `Copy items if needed` and `Create groups`.
+
+## Usage
+
+To show QRCode scanner:
+
+```swift
+let qrCodeController = SPQRCodeViewController()
+
+qrCodeController.cameraFoundHandler = { value in
+    print(value)
+}
+
+viewController.present(qrCodeController, animated: true, completion: nil)
+```
+
+If need with specific view for frame and preview, use this:
+
+```swift
+let frameView = UIView()
+frameView.layer.borderWidth = 3.0
+
+let previewLabel = UILabel()
+
+let qrCodeController = SPQRCodeViewController()
+qrCodeController.customFrameView = frameView
+qrCodeController.customPreviewView = previewLabel
+
+qrCodeController.cameraFoundHandler = { [weak previewLabel] value in
+    previewLabel?.text = value
+}
+
+viewController.present(qrCodeController, animated: true, completion: nil)
+```
+
+Optionaly you can create subclass of `SPQRCodeViewController` for more control