Add download count

README.md

@@ -5,6 +5,10 @@ Greenlock™ for Express.js
 
 An easy-to-use ACME client for Free SSL and Automated HTTPS.
 
+!["Lifetime Downloads"](https://img.shields.io/npm/dt/greenlock.svg "Lifetime Download Count (can't be shown)")
+!["Monthly Downloads"](https://img.shields.io/npm/dm/greenlock.svg "Monthly Download Count (can't be shown)")
+!["Weekly Downloads"](https://img.shields.io/npm/dw/greenlock.svg "Weekly Download Count (can't be shown)")
+
 | Sponsored by [ppl](https://ppl.family) |
 [Greenlock™](https://git.coolaj86.com/coolaj86/greenlock.js) for
 [cli](https://git.coolaj86.com/coolaj86/greenlock-cli.js),