Add screenshots to Readme

+# 1.3.2
+* Update Readme
+
 # 1.3.1
 * Fix pana linting notices
 

@@ -8,7 +8,9 @@ This library is divided in two parts:
 It can create a full multi-pages document with graphics,
 images and text using TrueType fonts. With the ease of use you already know.
 
-> Use `printing` package <https://pub.dartlang.org/packages/printing>
+![Example document](example.jpg)
+
+> Use the `printing` package <https://pub.dartlang.org/packages/printing>
 > for full flutter print and share operation.
 
 The coordinate system is using the internal Pdf unit:

@@ -2,7 +2,7 @@ name: pdf
 author: David PHAM-VAN <dev.nfet.net@gmail.com>
 description: A pdf producer for Dart. It can create pdf files for both web or flutter.
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/pdf
-version: 1.3.1
+version: 1.3.2
 
 environment:
   sdk: ">=1.8.0 <3.0.0"

+# 1.3.3
+* Update Readme
+
 # 1.3.2
 * Fix iOS printing issues
 

@@ -5,6 +5,8 @@ documents to android or ios compatible printers
 
 See the example on how to use the plugin.
 
+<img alt="Example document" src="example.png" width="300">
+
 > This plugin uses the `pdf` package <https://pub.dartlang.org/packages/pdf>
 > for pdf creation. Please refer to <https://pub.dartlang.org/documentation/pdf/latest/>
 > for documentation.

@@ -2,7 +2,7 @@ name: printing
 author: David PHAM-VAN <dev.nfet.net@gmail.com>
 description: Plugin that allows Flutter apps to generate and print documents to android or ios compatible printers
 homepage: https://github.com/DavBfr/dart_pdf/tree/master/printing
-version: 1.3.2
+version: 1.3.3
 
 environment:
   sdk: ">=1.19.0 <3.0.0"