Update README: replace installation instructions

Author: LukasPoque

README.md

@@ -38,15 +38,7 @@ For further information see the [KWH Glossar](https://www.kwh40.de/glossar/) and
 
 ## Installing
 
-Add it to your `pubspec.yaml` file:
-```yaml
-dependencies:
-  s3i_flutter: ^0.2.1
-```
-Install packages from the command line
-```
-flutter packages get
-```
+Please see [Pub.dev](https://pub.dev/packages/s3i_flutter/install) for instructions how to install this package to your flutter app. 
 
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 a like on [pub.dev](https://pub.dev/packages/s3i_flutter) :heart: