Fix: Update slack links (#1426)

.github/config.yml

@@ -4,7 +4,7 @@
 
 # Comment to be posted to on first time issues
 newIssueWelcomeComment: >
-  Thanks for opening your first issue in this project! If you haven't already, you can [join our slack](https://docs.google.com/forms/d/e/1FAIpQLSczZbZB9ql_Xl-1uBtmvYmA0fwfm1UX92SyWAdkuMEDfxac5w/viewform) and join the #gtfs-validators channel to meet our awesome community. Come say hi :wave:!
+  Thanks for opening your first issue in this project! If you haven't already, you can [join our slack](https://share.mobilitydata.org/slack) and join the #gtfs-validators channel to meet our awesome community. Come say hi :wave:!
   <br><br> Welcome to the community and thank you for your engagement in open source! :tada:
   <br><br> ![](https://media.giphy.com/media/l2JHZ0dIcyFo5UQGQ/giphy.gif)
 

README.md

@@ -1,5 +1,5 @@
 # Canonical GTFS Schedule Validator
-[![Test Package Document](https://github.com/MobilityData/gtfs-validator/workflows/Test%20Package%20Document/badge.svg)](https://github.com/MobilityData/gtfs-validator/actions?query=workflow%3A%22Test+Package+Document%22) ![End to end](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end/badge.svg) ![End to end big](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end%20big/badge.svg) ![End to end 100](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end%20100/badge.svg) [![Rule acceptance tests](https://github.com/MobilityData/gtfs-validator/actions/workflows/acceptance_test.yml/badge.svg)](https://github.com/MobilityData/gtfs-validator/actions/workflows/acceptance_test.yml) ![Docker image](https://github.com/MobilityData/gtfs-validator/actions/workflows/docker.yml/badge.svg) [![Join the gtfs-validator chat](https://badgen.net/badge/slack/%20/green?icon=slack)](https://bit.ly/mobilitydata-slack)
+[![Test Package Document](https://github.com/MobilityData/gtfs-validator/workflows/Test%20Package%20Document/badge.svg)](https://github.com/MobilityData/gtfs-validator/actions?query=workflow%3A%22Test+Package+Document%22) ![End to end](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end/badge.svg) ![End to end big](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end%20big/badge.svg) ![End to end 100](https://github.com/MobilityData/gtfs-validator/workflows/End%20to%20end%20100/badge.svg) [![Rule acceptance tests](https://github.com/MobilityData/gtfs-validator/actions/workflows/acceptance_test.yml/badge.svg)](https://github.com/MobilityData/gtfs-validator/actions/workflows/acceptance_test.yml) ![Docker image](https://github.com/MobilityData/gtfs-validator/actions/workflows/docker.yml/badge.svg) [![Join the gtfs-validator chat](https://badgen.net/badge/slack/%20/green?icon=slack)](https://share.mobilitydata.org/slack)
 
 
 A [General Transit Feed Specification (GTFS) Schedule](https://gtfs.mobilitydata.org/spec/gtfs-schedule) (static) feed validator, maintained by [MobilityData](www.mobilitydata.org). 

docs/CONTRIBUTING.md

@@ -24,7 +24,7 @@ There are many ways to contribute to this project: improving code and documentat
 
 
 ## MobilityData slack
-To join the slack, please fill this ["Request to join"](https://docs.google.com/forms/d/e/1FAIpQLSczZbZB9ql_Xl-1uBtmvYmA0fwfm1UX92SyWAdkuMEDfxac5w/viewform) form. Then, you will receive your invitation via the e-mail provided. 
+[Here is a link](https://share.mobilitydata.org/slack) to join our slack.
 After joining, you can add the `gtfs-validators` channel and introduce yourself there. This channel is dedicated to the GTFS Schedule and Realtime validators, and this is where users can ask questions, share their intention to contribute, and receive any important news. 
 
 ## Contributor meeting