[docs] Make Ray slack more prominent (#7870)

doc/source/installation.rst

@@ -1,8 +1,9 @@
 Installing Ray
 ==============
 
-Ray currently supports MacOS and Linux. Windows support
-is planned for the future.
+.. important:: Join our `community slack <https://forms.gle/9TSdDYUgxYs8SA9e8>`_ to discuss Ray!
+
+Ray currently supports MacOS and Linux. Windows support is planned for the future.
 
 Latest stable version
 ---------------------

doc/source/raysgd/raysgd.rst

@@ -16,6 +16,8 @@ The main features are:
   This API is new and may be revised in future Ray releases. If you encounter
   any bugs, please file an `issue on GitHub`_.
 
+.. important:: Join our `community slack <https://forms.gle/9TSdDYUgxYs8SA9e8>`_ to discuss Ray!
+
 
 Getting Started
 ---------------

doc/source/rllib.rst

@@ -7,6 +7,8 @@ RLlib is an open-source library for reinforcement learning that offers both high
 
 To get started, take a look over the `custom env example <https://github.com/ray-project/ray/blob/master/rllib/examples/custom_env.py>`__ and the `API documentation <rllib-toc.html>`__. If you're looking to develop custom algorithms with RLlib, also check out `concepts and custom algorithms <rllib-concepts.html>`__.
 
+.. important:: Join our `community slack <https://forms.gle/9TSdDYUgxYs8SA9e8>`_ to discuss Ray/RLlib!
+
 RLlib in 60 seconds
 -------------------
 

doc/source/tune.rst

@@ -17,6 +17,8 @@ Tune is a Python library for experiment execution and hyperparameter tuning at a
 .. _`Vizier's Median Stopping Rule`: tune-schedulers.html#median-stopping-rule
 .. _`HyperBand/ASHA`: tune-schedulers.html#asynchronous-hyperband
 
+.. important:: Join our `community slack <https://forms.gle/9TSdDYUgxYs8SA9e8>`_ to discuss Ray!
+
 For more information, check out:
 
   * `Code <https://github.com/ray-project/ray/tree/master/python/ray/tune>`__: GitHub repository for Tune.