Replace plutus-playground with demeter.run (#910)

* remove references to plutus-playground

Remove references to the plutus playground as it is no longer maintained and instead add a section about Demeter.run

* Move demeter to bottom

* tone down demeter text

Co-authored-by: Robert Phair <[email protected]>

docs/smart-contracts/plutus.md

@@ -27,16 +27,8 @@ Jann Müller then takes us through the Plutus Application Platform, where assets
 
 <iframe width="100%" height="325" src="https://www.youtube.com/embed/usMPt8KpBeI" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture fullscreen"></iframe>
 
-## Plutus Playground
-The Plutus Playground is a code editor and simulator in one.
-
-[![Plutus Playground](../../static/img/get-started/smart-contracts/plutus-playground.jpg)](https://playground.plutus.iohkdev.io)
-
-There is a written tutorial on [how to compile and test a Plutus App](https://plutus-apps.readthedocs.io/en/latest/plutus/tutorials/plutus-playground.html) or you can watch this video tutorial:   
-<iframe width="100%" height="325" src="https://www.youtube.com/embed/DhRS-JvoCw8" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture fullscreen"></iframe>
-
 ## Further Tutorials
-- [Writing a basic Plutus app in the Plutus Playground](https://plutus-apps.readthedocs.io/en/latest/plutus/tutorials/basic-apps.html)
+- [Writing a basic Plutus app](https://plutus-apps.readthedocs.io/en/latest/plutus/tutorials/basic-apps.html)
 - [Using Plutus Tx](https://plutus.readthedocs.io/en/latest/tutorials/plutus-tx.html)
 - [Writing basic validator scripts](https://plutus.readthedocs.io/en/latest/tutorials/basic-validators.html)
 - [Writing basic minting policies](https://plutus.readthedocs.io/en/latest/tutorials/basic-minting-policies.html)
@@ -66,3 +58,9 @@ Prior knowledge of Haskell or functional programming is also recommended, as Plu
 - [Apply for the Plutus Pioneer Program](https://testnets.cardano.org/en/plutus-pioneer-program/)
 
 You can also check out the book "Plutus - Learning a smart-contract language" that follows the 3rd iteration of the Plutus pioneer programm and contains all code examples from the course. The book is availabe at this repository: https://github.com/LukaKurnjek/plutus-pioneer-program.
+
+## Demeter
+
+Demeter is a web-based development platform providing a full suite of tools for building Cardano dApps end-to-end. It features starter-kits for a range of different project types including Plutus: [Plutus Starter Kit](https://github.com/txpipe/plutus-starter-kit).
+
+[Demeter.run](https://demeter.run) provides a free tier of their service where you can get started experimenting with Plutus.