Update README.md

Add REST API, rephrase intro

Author: unixpi

README.md

@@ -8,7 +8,7 @@
 [![Discord: Nimbus](https://img.shields.io/badge/discord-nimbus-orange.svg)](https://discord.gg/XRxWahP)
 [![Status: #nimbus-general](https://img.shields.io/badge/status-nimbus--general-orange.svg)](https://join.status.im/nimbus-general)
 
-Nimbus-eth2 is a extremely efficient Beacon Chain client for participating in the Ethereum Proof of Stake protocol. It performs well on embedded systems, resource-restricted devices -- including Raspberry Pis and mobile devices -- the low resource usage also makes it an excellet choice for running together with an Ethereum client on a server or a desktop where it simply takes up less resources.
+Nimbus-eth2 an extremely efficient consensus layer (eth2) client implementation. It performs well on embedded systems and resource-restricted devices -- including Raspberry Pis and mobile devices. It's low resource usage also makes it an excellet choice for running together with an Ethereum client on a server or a desktop (where it simply takes up less resources). 
 
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@@ -33,7 +33,18 @@ Nimbus-eth2 is a extremely efficient Beacon Chain client for participating in th
 
 You can find the information you need to run a beacon node and operate as a validator in [The Book](https://nimbus.guide/).
 
-The [Quickstart](https://nimbus.guide/quick-start.html) in particular will help you get connected to the Pyrmont Testnet and eth2 Mainnet quickly!
+The [Quickstart](https://nimbus.guide/quick-start.html) in particular will help you quickly connect to either mainnet or the Prater testnet.
+
+## Quickly test your tooling against Nimbus
+
+ The [Nimbus REST api](https://nimbus.guide/rest-api.html) is now available from:
+ 
+* http://testing.mainnet.beacon-api.nimbus.team/
+* http://unstable.mainnet.beacon-api.nimbus.team/
+* http://unstable.prater.beacon-api.nimbus.team/
+
+
+Note that right now these are very much unstable testing instances. They may be unresponsive at times - so **please do not rely on them for validation**. We may also disable them at any time.
 
 ## Related projects