Update README with new "Support us" section

Author: AdrianMrn

README.md

@@ -13,6 +13,15 @@ The [Open Graph protocol](http://ogp.me/) protocol provides a way to add rich so
 
 This package provides a fluent builder for these Open Graph objects as specified in the [official RDF schema](http://ogp.me/ns/ogp.me.ttl).
 
+## Support us
+
+Learn how to create a package like this one, by watching our premium video course:
+
+[![Laravel Package training](https://spatie.be/github/package-training.jpg)](https://laravelpackage.training)
+
+We invest a lot of resources into creating [best in class open source packages](https://spatie.be/open-source). You can support us by [buying one of our paid products](https://spatie.be/open-source/support-us).
+
+We highly appreciate you sending us a postcard from your hometown, mentioning which of our package(s) you are using. You'll find our address on [our contact page](https://spatie.be/about-us). We publish all received postcards on [our virtual postcard wall](https://spatie.be/open-source/postcards).
 
 ## Postcardware