Suggest adt installation (#662)

Co-authored-by: Don Naro <dnaro@redhat.com>
Co-authored-by: Matt Martz <matt@sivel.net>

docs/installation.rst

@@ -18,8 +18,16 @@ Install from PyPI
 
 .. code-block:: shell
 
-   $ pip install ansible-builder
+   $ pip3 install ansible-builder
 
+.. note::
+
+   An **alternative** approach to installing ``ansible-builder`` is using the ``ansible-dev-tools`` package. `Ansible Development Tools (ADT) <https://ansible.readthedocs.io/projects/dev-tools/>`_ is a single Python package that includes all necessary tools to set up a development environment, generate new collections, build and test the content.
+
+   .. code-block:: shell
+
+      # This also installs ansible-core if it is not already installed
+      $ pip3 install ansible-dev-tools
 
 Install from Source
 *******************
@@ -28,10 +36,10 @@ To install from the mainline development branch:
 
 .. code-block:: shell
 
-   $ pip install https://github.com/ansible/ansible-builder/archive/devel.zip
+   $ pip3 install https://github.com/ansible/ansible-builder/archive/devel.zip
 
 To install from a specific tag or branch, replace :code:`<ref>` in the following example:
 
 .. code-block:: shell
 
-   $ pip install https://github.com/ansible/ansible-builder/archive/<ref>.zip
+   $ pip3 install https://github.com/ansible/ansible-builder/archive/<ref>.zip

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = linters, unit
+envlist = linters, unit, docs
 isolated_build = True
 
 [shared]