Revert "Update Slack url" (#2034)

* Revert "Update Slack url (#2025)"

This reverts commit c48670ccdc.

README.md

@@ -7,7 +7,7 @@
 **Open Source Wealth Management Software**
 
 [**Ghostfol.io**](https://ghostfol.io) | [**Live Demo**](https://ghostfol.io/en/demo) | [**Ghostfolio Premium**](https://ghostfol.io/en/pricing) | [**FAQ**](https://ghostfol.io/en/faq) |
-[**Blog**](https://ghostfol.io/en/blog) | [**Slack**](https://ghostfolio.slack.com) | [**Twitter**](https://twitter.com/ghostfolio_)
+[**Blog**](https://ghostfol.io/en/blog) | [**Slack**](https://join.slack.com/t/ghostfolio/shared_invite/zt-vsaan64h-F_I0fEo5M0P88lP9ibCxFg) | [**Twitter**](https://twitter.com/ghostfolio_)
 
 [![Shield: Buy me a coffee](https://img.shields.io/badge/Buy%20me%20a%20coffee-Support-yellow?logo=buymeacoffee)](https://www.buymeacoffee.com/ghostfolio)
 [![Shield: Contributions Welcome](https://img.shields.io/badge/Contributions-Welcome-orange.svg)](#contributing)
@@ -269,7 +269,7 @@ Deprecated: `GET http://localhost:3333/api/v1/auth/anonymous/<INSERT_SECURITY_TO
 
 Ghostfolio is **100% free** and **open source**. We encourage and support an active and healthy community that accepts contributions from the public - including you.
 
-Not sure what to work on? We have got some ideas. Please join the Ghostfolio [Slack](https://ghostfolio.slack.com) channel or tweet to [@ghostfolio\_](https://twitter.com/ghostfolio_). We would love to hear from you.
+Not sure what to work on? We have got some ideas. Please join the Ghostfolio [Slack](https://join.slack.com/t/ghostfolio/shared_invite/zt-vsaan64h-F_I0fEo5M0P88lP9ibCxFg) channel or tweet to [@ghostfolio\_](https://twitter.com/ghostfolio_). We would love to hear from you.
 
 If you like to support this project, get [**Ghostfolio Premium**](https://ghostfol.io/en/pricing) or [**Buy me a coffee**](https://www.buymeacoffee.com/ghostfolio).