update gitter link to slack link

wirthi · wirthi · commit 545d323b29e1 · 2020-02-26T13:55:52.000+01:00
diff --git a/README.md b/README.md
@@ -1,4 +1,4 @@
-[![Join the chat at https://gitter.im/graalvm/graaljs](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/graalvm/graaljs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![https://graalvm.slack.com](https://img.shields.io/badge/slack-join%20channel-active)](https://www.graalvm.org/slack-invitation/)
 
 A high performance implementation of the JavaScript programming language.
 Built on the GraalVM by Oracle Labs.

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-[![Join the chat at https://gitter.im/graalvm/graaljs](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/graalvm/graaljs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)`
	`1`	`+[![https://graalvm.slack.com](https://img.shields.io/badge/slack-join%20channel-active)](https://www.graalvm.org/slack-invitation/)`
`2`	`2`
`3`	`3`	`A high performance implementation of the JavaScript programming language.`
`4`	`4`	`Built on the GraalVM by Oracle Labs.`