Improve the visibility of Discord channel in README.md (#1182)

Discord badge now better matches dimensions and style of the other badges.

Added Discord as the community entry in the table of contents.

I've removed the link to the gitter since it was never used and likely never will be.

README.rst

@@ -18,17 +18,14 @@ Subtitles, faster than your thoughts.
     :target: https://github.com/Diaoul/subliminal/blob/master/LICENSE
     :alt: License
 
-.. image:: https://img.shields.io/badge/gitter-join%20chat-1dce73.svg
-    :alt: Join the chat at https://gitter.im/Diaoul/subliminal
-    :target: https://gitter.im/Diaoul/subliminal
-
-.. image:: https://img.shields.io/discord/1256603445411184740?style=for-the-badge&label&logo=discord&logoColor=white&color=blue
+.. image:: https://img.shields.io/badge/discord-7289da.svg?style=flat-square&logo=discord
     :alt: Discord
     :target: https://discord.gg/kXW6sWte9N
 
 
 :Project page: https://github.com/Diaoul/subliminal
 :Documentation: https://subliminal.readthedocs.org/
+:Community: https://discord.gg/kXW6sWte9N
 
 
 Usage
@@ -71,6 +68,7 @@ Download best subtitles in French and English for videos less than two weeks old
 
 Docker
 ^^^^^^
+
 Run subliminal in a docker container::
 
     $ docker run --rm --name subliminal -v subliminal_cache:/usr/src/cache -v /tvshows:/tvshows -it diaoulael/subliminal download -l en /tvshows/The.Big.Bang.Theory.S05E18.HDTV.x264-LOL.mp4
@@ -94,10 +92,22 @@ clone your fork locally and install a development version::
     $ pip install --user -e '.[dev,test,docs]'
 
 
-Nautilus/Nemo integration
--------------------------
-See the dedicated `project page <https://github.com/Diaoul/nautilus-subliminal>`_ for more information.
+Integrations
+------------
+Subliminal integrates with various desktop file managers to enhance your workflow:
+
+- **Nautilus/Nemo**: See the dedicated `project page <https://github.com/Diaoul/nautilus-subliminal>`_ for more information.
+- **Dolphin**: See this `Gist <https://gist.github.com/maurocolella/03a9f02c56b1a90c64f05683e2840d57>`_. for more details.
+
+Contributing
+------------
+We welcome contributions from the community! If you're interested in contributing, here are a few
+ways you can get involved:
+
+- **Browse Issues and Pull Requests**: Check out the existing `Issues <https://github.com/Diaoul/subliminal/issues>`_
+  and `Pull Requests <https://github.com/Diaoul/subliminal/pulls>`_ to see where you can help.
+- **Report Bugs or Request Features**: If you encounter a bug or have a feature request, please create a GitHub Issue.
+- **Follow the Contribution Guide**: For detailed instructions on how to contribute, please refer to our
+  `Contribution Guide <https://github.com/Diaoul/subliminal/blob/main/CONTRIBUTING.md>`_.
 
-Dolphin integration
--------------------
-See this `Gist <https://gist.github.com/maurocolella/03a9f02c56b1a90c64f05683e2840d57>`_.
+Your contributions are greatly appreciated and help make this project better for everyone!