Update documentation.

README.md

@@ -2,6 +2,45 @@
 
 This project intends to be a small wrapper around C++ code from https://github.com/nayuki/QR-Code-generator in order to be able to use it with Swift easily.
 
+### Build it
+#### Swift Package Manager
+1. `git clone [email protected]:fjfdeztoro/Swift-QR-Code-generator.git`
+2. `cd cd Swift-QR-Code-generator/`
+3. `swift build && swift test`
+
+#### With Xcode
+All the steps from previous entry and:
+1. `swift package generate-xcodeproj`
+2. `open QRCodeGenerator.xcodeproj/`
+3. `Select target: QRCodeGenerator-Package`
+4. `Go to Build Settings for the project.`
+5. `Select All`
+6. `Look for Apple LLVM - Language - C++ section`
+7. `Change C++ Language Dialect to C++11[-std=c++11]`
+8. `Change C++ Standard Library to libc++`
+9. `cmd+b`
+
+### Use it
+#### Resolving dependencies
+In your `Package.swift` add this entry as a new dependency:
+```
+.package(url: "https://github.com/fjfdeztoro/Swift-QR-Code-generator.git", from: "0.0.2")
+```
+
+And in your target, add this dependency: `"QRCodeGenerator"`
+
+#### Mixing it with your code.
+
+```
+import QRCodeGenerator
+print(QRCodeGenerator.getQRCodeAsSVG("https://github.com/fjfdeztoro/Swift-QR-Code-generator/blob/master/README.md", withTolerance: .High))
+
+```
+
+That code will print the content of a SVG file that will contain a QR with a URL to this file.
+
+![Demo screenshot][1]
+
 ## License
 MIT License.
 
@@ -10,3 +49,5 @@ Permission is hereby granted, free of charge, to any person obtaining a copy of
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 
 * The Software is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the Software or the use or other dealings in the Software.
+
+[1]: ./art/qr-to-readme.png