Add development environment docs (#1633)

Signed-off-by: Bryce Gattis <[email protected]>

CONTRIBUTING.md

@@ -1,5 +1,7 @@
 # Contributing To Rez
 
+## Guidelines
+
 If you would like to contribute code you can do so through GitHub by forking the repository and
 sending a pull request. Please follow these guidelines:
 
@@ -21,6 +23,45 @@ sending a pull request. Please follow these guidelines:
     document the setting. The comments in this file are extracted and turned into documentation. Pay
     attention to the comment formatting and follow the existing style closely.
 
+## Development Environment
+
+### Prerequisites 
+
+On Windows, make sure to set your PowerShell execution policy as shown [here](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy?view=powershell-5.1),
+otherwise the PowerShell tests will fail.
+
+### Setting Up
+
+To begin development on rez you'll first need to set up your development environment. There are many 
+ways you can do it, but these are the recommended approaches.
+
+This first approach will automatically create a virtual environment for you, patch the Rez binaries, 
+and copy completion scripts. All tests will be run this way.
+
+1. Fork the repo and clone it.
+2. Create a new Git branch and check it out.
+3. Install your local rez code by running `python install.py venv`.
+4. Activate the virtual environment by running the `activate` file.
+5. Add the `Scripts/rez` folder on Windows or the `bin/rez` folder on Mac/Linux to the `PATH` environment variable.
+
+There is an alternative method of setting up your development environment, that doesn't use the `install.py`
+script. Please note that not all tests will be run if rez is installed this way.
+
+1. Fork the repo and clone it.
+2. Create a new Git branch and check it out.
+3. Create a virtual environment in the same directory as the repo by running `python -m venv venv`.
+4. Activate the virtual environment by running the `activate` file.
+5. Pip install your local rez code by running `pip install .`.
+
+Additionally, if you are going to run tests in the repo, you may want to install two additional optional 
+packages for improved test output: `pytest` and `parameterized`. You can install these by running 
+`pip install pytest parameterized`.
+
+### Running Tests
+
+1. Set up your development environment as shown above.
+2. Run `rez selftest`.
+
 ## CLA
 
 Rez enforces use of a Contributor License Agreement as per ASWF guidelines. You need only sign up to the EasyCLA system once, but until you do, your PRs will be automatically blocked.