Update the docs

Author: mdmintz

README.md

@@ -81,6 +81,7 @@ pip install seleniumbase
 
 > (Add ``--upgrade`` OR ``-U`` to upgrade an installation.)
 > (Add ``--force-reinstall`` to upgrade dependencies.)
+> (Use ``pip3`` if multiple versions of Python are installed.)
 
 🔵 You can also install ``seleniumbase`` from a [GitHub](https://github.com/seleniumbase/SeleniumBase) clone:
 

mkdocs.yml

@@ -107,6 +107,7 @@ nav:
     - Presenter Demo: https://seleniumbase.io/other/presenter.html
     - Core Presentation: https://seleniumbase.io/other/core_presentation.html
     - Chart Maker Demo: https://seleniumbase.io/other/chart_presentation.html
+    - Virtual Env Tutorial: https://seleniumbase.io/other/py_virtual_envs.html
   - Thank You: help_docs/thank_you.md
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