SM-1098: Update Python Wrapper README Instructions (#592)

## Type of change

<!-- (mark with an `X`) -->

```
- [ ] Bug fix
- [ ] New feature development
- [ ] Tech debt (refactoring, code cleanup, dependency upgrades, etc)
- [ ] Build/deploy pipeline (DevOps)
- [x] Other
```

## Objective

<!--Describe what the purpose of this PR is. For example: what bug
you're fixing or what new feature you're adding-->

Update the Python Wrapper README, now that we are using
[maturin](https://pypi.org/project/maturin).

languages/python/.gitignore

@@ -1,3 +1,4 @@
 *.egg-info
 bitwarden_py*.so
 __pycache__
+.venv

languages/python/README.md

@@ -33,3 +33,26 @@ Set the `ORGANIZATION_ID` and `ACCESS_TOKEN` environment variables to your organ
 ```bash
 python3 ./example.py
 ```
+
+# Using Virtual Environments
+
+If you would like to build & run the script within a virtual environment you can do the following.
+
+## Build
+
+```bash
+npm run schemas # generate schemas.py
+
+cd languages/python/
+python3 -m venv .venv
+maturin develop
+```
+
+## Run
+
+```bash
+source .venv/bin/activate
+python3 ./example.py
+
+deactivate # run this to close the virtual session
+```