E2E test: README update for alternate interpreters

test/e2e/README.md

@@ -35,7 +35,7 @@ An [example test](https://github.com/posit-dev/positron/blob/main/test/e2e/examp
 
 ### Environment Variables
 
-In order to run the tests you'll need to have two environment variables set. These are so Positron knows what R and Python versions to load. A typical place to set them on a mac is in your `.zshrc`, but you should use your environment variable setting method of choice!
+In order to run the tests you'll need to have four environment variables set. These are so Positron knows what R and Python versions to load. A typical place to set them on a mac is in your `.zshrc`, but you should use your environment variable setting method of choice!
 
 Make sure you have the selected R and Python version installed that you are using for the environment variables. The easiest way is to open Positron and copy a version number you have available in the interpreter picker.
 
@@ -44,8 +44,12 @@ Add these to your .zshrc or the relevant configuration file for your shell:
 ```bash
 export POSITRON_PY_VER_SEL="3.11.5"
 export POSITRON_R_VER_SEL="4.2.1"
+export POSITRON_PY_ALT_VER_SEL='3.13.0 (Pyenv)'
+export POSITRON_R_ALT_VER_SEL='4.4.2'
 ```
 
+_Note: The environment variables with `ALT` in them are for the alternate interpreters which are used in fewer tests and might not be immediatly needed. If you are using Pyenv for your alternate Python interpreter, please add ` (Pyenv)` to the variable value._
+
 _Note: If you forgot to set the environment variables before running the tests, you'll need to restart your editor or shell session for the environment variables to be loaded in._
 
 ## Dependencies