create stub for EARLY TESTERS

docs/EARLY_TESTERS.md

+# EARLY TESTERS PROGRAMME
+
+## What is it?
+
+## What are the expectations?
+
+## Who has signed up?
+
+- Infura
+- Textile
+
+## How to sign up?
+
+Simply submit a PR to this document by adding your project name and contact.