Update README.md to solicit input on EOL Rubies

Announce timeframe of Feb 1st 2021 to decide whether to continue
to support any EOL Ruby versions (< 2.5 as of today Jan 13 2021), and
if so which ones.

Direct comments to issue #58.

README.md

@@ -1,3 +1,8 @@
+## ⚠️WARNING⚠️, 🔴IMPORTANT❗🔴
+### Using Docile on an end-of-life Ruby version (< **2.5**)?
+#### Please comment on [issue #58](https://github.com/ms-ati/docile/issues/58) this month 📅!
+We'll decide which Ruby versions to continue supporting on **Feb 1st 2021**.
+
 # Docile
 
 [![Gem Version](https://img.shields.io/gem/v/docile.svg)](https://rubygems.org/gems/docile)