Update README.md (#2158)

* Cache Discord Badge to avoid upstream rate limiting

## Summary

## How was it tested?
Need to see if rate limiting drops after publishing

Signed-off-by: John Lago <[email protected]>

Author: Lagoja

README.md

@@ -8,7 +8,7 @@
 
 ### Instant, easy, and predictable development environments
 
-[![Join Discord](https://img.shields.io/discord/903306922852245526?color=7389D8&label=discord&logo=discord&logoColor=ffffff)](https://discord.gg/jetify) ![License: Apache 2.0](https://img.shields.io/github/license/jetify-com/devbox) [![version](https://img.shields.io/github/v/release/jetify-com/devbox?color=green&label=version&sort=semver)](https://github.com/jetify-com/devbox/releases) [![tests](https://github.com/jetify-com/devbox/actions/workflows/cli-post-release.yml/badge.svg)](https://github.com/jetify-com/devbox/actions/workflows/cli-release.yml?branch=main) [![Built with Devbox](https://www.jetify.com/img/devbox/shield_galaxy.svg)](https://www.jetify.com/devbox/docs/contributor-quickstart/)
+[![Join Discord](https://img.shields.io/discord/903306922852245526?color=7389D8&label=discord&logo=discord&logoColor=ffffff&cacheSeconds=1800)](https://discord.gg/jetify) ![License: Apache 2.0](https://img.shields.io/github/license/jetify-com/devbox) [![version](https://img.shields.io/github/v/release/jetify-com/devbox?color=green&label=version&sort=semver)](https://github.com/jetify-com/devbox/releases) [![tests](https://github.com/jetify-com/devbox/actions/workflows/cli-post-release.yml/badge.svg)](https://github.com/jetify-com/devbox/actions/workflows/cli-release.yml?branch=main) [![Built with Devbox](https://www.jetify.com/img/devbox/shield_galaxy.svg)](https://www.jetify.com/devbox/docs/contributor-quickstart/)
 
 ## What is it?