Update Broken Carsus Chat Link to Matrix

[manas-dhyani]

Describe the Bug
Since Gitter has migrated its rooms to Matrix, the current chat link for Carsus (previously pointing to Gitter) is outdated or broken. Users trying to join the discussion are unable to access the correct chat room.

To Reproduce

1. Visit the Carsus documentation/homepage.
2. Click on the chat link (previously Gitter).
3. The link is either broken or redirects incorrectly.

Screenshots

System

• OS:

  • GNU/Linux
  • macOS

• Environment (conda list):

Additional Context
The chat link should be updated to the correct Matrix room: Matrix TARDIS-Carsus.