Update README with supported Erlang/OTP versions

README.md

@@ -1,6 +1,6 @@
 # Rebar3
 
-![Build Status](https://github.com/erlang/rebar3/workflows/Common%20Test/badge.svg)
+[![Build Status](https://github.com/erlang/rebar3/workflows/Common%20Test/badge.svg)](https://github.com/erlang/rebar3/actions?query=branch%3Amaster+workflow%3A"Common+Test") [![Erlang Versions](https://img.shields.io/badge/Supported%20Erlang%2FOTP-19.0%20to%2023.0-blue)](http://www.erlang.org)
 
 1. [What is Rebar3?](#what-is-rebar3)
 2. [Why Rebar3?](#why-rebar3)
@@ -94,6 +94,8 @@ by [Erlang Solutions](https://www.erlang-solutions.com/resources/download.html),
 but be sure to choose the "Standard" download option or you'll have issues building
 projects.
 
+Do note that if you are planning to work with multiple Erlang versions on the same machine, you will want to build Rebar3 with the oldest one of them. The five newest major Erlang releases are supported at any given time: if the newest version is OTP-23, building with versions as old as OTP-19 will be supported, and produce an executable that will work with those that follow.
+
 ## Documentation
 
 Rebar3 documentation is maintained on [https://www.rebar3.org/docs](https://www.rebar3.org/docs)