Indicate zshenv is to be used when configuring ZSH version managers

[justinbburris]

Motivation

Closes #2202

When configuring your ZSH based shell, we want to make sure the right file is indicated.

Implementation

Tested the tool via booting up the extension in VS Code.

Automated Tests

They're just readme changes, so modification of features.

Manual Tests

(I used rbenv for as my ruby version manager)

• Enable your ruby version manager in ZSH, using zshrc, and open VS Code. You'll see the extension fail to initialize
• Enable your ruby version manager in ZSH, using zshenv, and open VS Code. You'll see the extension initialize

[github-actions[bot]]

This pull request is being marked as stale because there was no activity in the last 2 months