Improve install docs by mentioning how to actually download rez (#1660)

Signed-off-by: Jean-Christophe Morin <jean_christophe_morin@hotmail.com>

docs/source/installation.rst

@@ -5,15 +5,20 @@ Installation
 Installation Script
 ===================
 
-.. warning::
-   The install script only supports Python 3.7+.
+To install rez, you will need:
+
+1. Python 3.7 or above. We support 3.7, 3.8, 3.9, 3.10 and 3.11.
+   The python interpreter you use to run the install script will be the interpreter
+   used by rez itself.
+2. The source code. You can get it by either cloning the `repository <https://github.com/AcademySoftwareFoundation/rez>`_
+   with git or downloading it from the `latest release <https://github.com/AcademySoftwareFoundation/rez/releases/latest>`_.
+   If you download rez from the release page on GitHub, don't forget to unpack the downloaded archive.
 
-To install rez, download the source. Then from the root directory, run::
+Then from the root directory, run::
 
    ]$ python ./install.py
 
-This installs rez to ``/opt/rez``. See ```install.py -h``` for how to install to a
-different location.
+This installs rez to ``/opt/rez``. Use ``install.py -h`` to see the different install options.
 
 Once the installation is complete, a message tells you how to run it::